REESE LIBRARY
UNIVERSITY OF CALIFORNIA.
Deceive J 7u^t£_
IB
Accession No. y^6 / 6 / • C7//-5N No.
RAILWAY "BLOCK11 SIGNALLING
THE PRINCIPLES OF TRAIN SIGNALLING
APPARATUS FOR ENSURING SAFETY.
JAMES PIGG, A.I.E.E.
ILLUSTRATED.
LONDON :
):it;c;s AM> CO., 139-140, SALISBURY COURT, FLEET STREET, B.C.
DEDICATION.
To THE AUTHOR'S FATHER.
(AN "I. O U.")
IRE
A considerable portion of this book appeared as a serial in Tfo
Electrical Engineer during the latter half of 1896. Since then the
matter has been revised and considerably extended by the inclusion of
descriptions of other apparatus, and by the insertion of examples of the
codes used, and the regulations and rules under which signalling is
carried out.
Railway signalling appears to have now reached a stage at which some
departure from the present methods seems probable. The lines upon
which changes will be made will, in all probability, result in a greater
degree of automatic control than obtains at present. The degree of
control is, however, difficult to predict ; and, moreover, the degree of
such control desirable is a debatable subject.
A study of the lines along which developments are proceeding shows
at least two marked divisions. In one, the apparatus is entirely auto-
matic ; in the other, the apparatus is so inter -connected with the
operations involved in the movement of traffic, as to act as a check
upon the actions of the controller of the traffic, for the time being, in
such respects as experience shows to be desirable. The first is by far
the more ambitious of the two, and adoption of such methods would
constitute a revolution in signalling. The second is the most adaptable
to present-day methods and apparatus. Which will be the survivor is
difficult to indicate, but completely automatic systems admit of none of
the selection which is the chief feature in the movement of heavy
traffic of mixed character.
The subject of signalling in all its branches is a most important one;
and it is because of this importance and the difficulty of thoroughly
estimating all the requirements in connection with railway signalling
without an accurate knowledge of details, that the author has included
the codes, regulations, and rules under which the work is carried out.
A glance at the records of the Patent Office speaks volumes for the
necessity of a study of detail before undertaking to supply apparatus for
a given purpose, or to meet such circumstances as have at some time
given rise to accident. The applicability of apparatus to all circum-
stances that experience shows may arise is of quite as much importance,
or more, than its applicability to circumstances which are the result of
neglect or inadvertence.
It only remains to be said that the author's thanks are due, and are
herewith gratefully tendered, to Mr. Preece, Messrs. Siemens, Messrs.
Saxby and Farmer, Mr. G. Edwards, Mr. W. R. Sykes, Mr. I. A.
Timmis, and others, for information respecting the apparatus they are
interested in, and to Mr. Clement E. Stretton for information respecting
the earlier days of railway signalling.
CONTENTS.
CHAPTER I.
Necessity for Regulation of Traffic — Historical Notes — Walker's System
of Bell Signalling — Mr. Edwin Clark's Recommendations — Methods of
Working Early Systems — Claims of Early Systems to be considered
" Block" Systems.
CHAPTER II.
Objects of Apparatus — Classification of Railway Signalling— Relative
Responsibility of Operators - Analysis of Electrical Signals— Codes, and
Rules and Regulations relating thereto — Block Indicators- Relative
Importance of Indications — Forms of Instruments— Classification of
Systems and Modes of Working — Disturbances of Instruments — Relative
Cost and Maintenance of Different Systems — Choice of Instruments.
CHAPTER III.
Train Messages and Instructions Use of Telephone — Outdoor Signal-
ling— Signal Whistles — Head Lights and Boards for Distinguishing.
Trains — Tail Lamps — Slip-Carriage Tail Lights — Hand Signals — Fixed
Signals — Fog Signalling— Mechanical Interlocking of Points and Signals —
Examples of Rules relating to Hand, Fixed, and Detonating Signals.
CHAPTER IV.
Alexander Bain's Signalling Instrument — "Absolute" and "Permissive"
Block Working— Single-Needle Block Instruments— Examples of Block
Sections and Circuit Arrangements — Four Hundred Yards' Rule— Switch-
ing Single-Needle Block Apparatus — Walker's Block Instrument — Preece's
Block Instrument — Harper's Block Instrument — Fletcher's Block Instru-
ment— Tyer's Block Instrument — Pigg's Arrangement for Locking Single-
Needle Instrument — Winter's Block Instrument and Winter and Craik's
Electrically Interlocked Semaphore — Saxby and Farmer's " Lock and
Block" Apparatus - Sykes's Block Instrument and Interlocking Appa-
ratus—Special Swingbridge Arrangements — Blakey and O'Donnell's
Interlocking for Single-Needle Instruments — Sykes and O'Donnell's
Interlocking for Single-Needle Instruments — Single- Line Working —
Simple Staff and Ticket — Staff and Ticket in Combination with Block
Working — Difference in Character of Single Lines — Webb and Thompson's
Train Staff Instruments— Tyer's Tablet Instruments— Differences in
Working by Tablet or Train Staff Instruments and Simple Staff and
Ticket- -Permissive Block Working, with Examples of Lines where
Applied— Single-Needle Instrument Applied to Permissive Block Work-
ing— Character of Indications — Disabilities- Tyer's Recording Instru-
CONTENTS.
merit — Hampson's Recording Instrument — Desirability of Providing
Records of Number of Trains in Section at Both Ends — Character of
Indication when Clearing Section of Trains.
CHAPTER V.
Gate Crossing Equipment for Single-Needle Block Circuits — Signal
Repeaters — Position of Contact Makers — Relative Positions of Signal
Lever, Signal Arm, and Repeater — Relative Importance of Indications —
Relative Advantages of Maintaining Indications by Continuous Currents,
or by Stability of Indicator — Signal Light Indicators and Alarms — Neces-
sity for Preserving Distinctive Character of Distant Signal during Dark-
ness— Stevens and Sons' Flash Light — Points' Indicators — Indicating
Condition of Section lietween Cabin and Advance Signal — Rail Indi-
cators— Momentary Contacts — Prolonged Contacts — Sykes's Electric
Fouling Bar— Sykes's Signal Selector — Inter-Cabin Electrical Inter-
locking, King's Cross and Belle Isle — Telephones on Block Circuits.
CHAPTER VI.
Causes Contributing to Accident — Irregularities in Working — Premature
Acceptance of Train — Sending Train Unsignalled— Instruments Designed
to Prevent these Errors — Disregard of Fixed Signals by Drivers— Fog
Signalling— Negative Character of "All Right" Signal — Dual Control
During Fog Signalling — Mechanical Apparatus for Placing Detonators in
Position for Explosion — Electrical Signalling to Drivers : By Bell on
Engine ; By Bell on Side of Line— Pigg's Suggestion for Signalling to
Drivers during Fogs, etc. — Raven and Baister's Apparatus for Signalling
to Drivers — General Application of such Methods — Necessity for more
General Repetition of Signals — Point to be Repeated — Desirability of
Uniform System and Apparatus — Apparatus to be Comprised in Term
" Block System" — Inter-Dependence of all Classes of Signals.
CHAPTER VII.
Mr. Alex. Siemens's Automatic Signalling System, Description 01
Apparatus — Application to Simple Section — Application to Junction
Working— Automatic Actuation of Points— Mr. I. A. Timmis's Automatic
Signalling System — Liverpool Overhead Railway — Signal Arrangements —
Vehicle Contacts for Operation — Currents used for Actuating Signals —
Description of Operations during Passage of Train through Sections —
Positions of Signals during Failure of Current — Cross-Over Road
Working — Terminal Station Arrangements — Cost of Actuation of
Signals — Timmis's Electrical Apparatus at Earl's Court Station — Actuation
of Points, Locking Bolts and Bars, Signals, and Ground Discs, and
Interlocking of Levers.
RAILWAY SIGNALLING.
CHAPTER I.
The " block " telegraph system in use for regulating
traffic is probably the most extensive of all the
adaptations of electricity to railway work, and its
"use-value" is undoubtedly greater than that of any
other form of electrical apparatus in use upon rail-
ways. The development of the " block " system has
been the work of the last thirty years approximately ;
previous to that time traffic was worked in quite a
different fashion to that in use at present.
The fundamental principle of the " block " was at
first derided, and the name chosen was considered as
characteristic of the condition traffic was likely to
get into under any such system of working. That
there should be any reason to prevent a driver from
proceeding as far as his visionary powers assured him
the line was clear, or that any train should be pre-
vented from " bumping " a preceding train — gently,
of course — was considered absurd, and there were not
wanting those who predicted the early demise of
this or any other system which involved restrictions
being put on the free passage of traffic. This, of
• course, was before the era of express trains travelling
at rates varying between 60 and 70 miles per hour.
i
2 RAILWAY SIGNALLING.
In those days it was no uncommon thing for agile
persons to boast of their ability to leave trains at
any point that was most suitable. At that date
railways were small concerns compared with what
they have, by extensions and amalgamations, now
become, and the volume of traffic handled by one
railway was correspondingly small.
The prophecies referred to have, however, been
falsified, and railway traffic is now carried with a
regularity and freedom from accident which is remark-
able when the quantity of material handled and the
area covered is taken into consideration. To this
precision, and the safety resulting therefrom, the
" block " has undoubtedly contributed quite as much
as any other branch of engineering.
Necessity for Regulating Traffic. — It was at a
very early period of railway history that the necessity
for some means of regulating and controlling the
passage of trains became apparent ; and electricity,
which was then really " in its infancy," as a means
of communication between those engaged in working
traffic, promised such excellent results, from the ease
with which it could be established and maintained,
and its comparative independence of distance, as led
to its early employment.
The time and place at which block working, as
known at present, was first introduced, is not known
with any certainty, owing to the vague accounts
available of the methods of working of the earlier
instances of the electrical signalling of trains. Most
of the earlier applications of electricity for this purpose
were brought into operation between special points on
RAILWAY SIGNALLING. 3
lines where the ordinary time interval, in use at other
places, was considered insufficient for the requirements
of that part of the line. Such places were those parts
of the line where tunnels were in use, or inclines, and
similar places. These were all isolated sections of
line ; other parts of the same line being worked
without any means of notifying the passage of trains
from point to point. Reliable records of the use of
electrical means of signalling are by no means
common, although its use for this purpose seems to
have been contemporaneous with the introduction of
electrical telegraphy. It is, however, by no means
certain that any of the earlier systems are entitled
to the name of " block," although the title is claimed
for many of them.
Much of this confusion arises, as already stated,
from the absence of the regulations defining the
methods of working adopted with the earlier systems ;
but part of it is undoubtedly due, also, to the want of
a definition of what is meant by the " block " system.
A study of the progress made, as shown by the scanty
records available, shows that, whilst the origination of
the main principle may be credited to some particular
person or persons, the means taken to carry out the
idea were of the most rudimentary character, and
were subject to considerable alteration and extension,
as the continual process of trial and error to which
they were subject showed to be necessary. There
would be no difficulty in defining the block system as
it is used to-day; but at what stage of its evolution
from the earlier methods to present-day practice, shall
the term "block" be first applied? Something like
i*
4 RAILWAY SIGNALLING.
fifty-seven years have passed since the first application
electricity to this purpose, and the progress from that
time to the present has been gradual and constant, and
is not yet completed.
Historic.— Mr. Clement E. Stretton, C.E., the
well-known expert on railway matters, in an
interesting letter to The Electrical Engineer of
November 13, 1896, throws considerable light on
the inception and development in its earlier stages
of what is now known as the "block" system, and,
as the result of his research, has shown that the
germ of the present system was brought into use
between Paddington, West Drayton, and Hanwell,
on the Great Western Railway, at the instance of
Cooke and Wheatstone, as early as December, 1839.
The system there brought into operation was an
adaptation of the ordinary telegraph system — the
departure and arrival of trains being telegraphed,
and instructions issued to stop a second train
on its arrival at any of the telegraph stations until
the arrival of the first train at the advance station
was telegraphed back. This is the earliest record
from official sources of the application of electricity
to the preservation of a space limit between succes-
sive trains on the same line of rails.
In 1840, as recorded in Mr. Langdon's "Applica-
tions of Electricity to Railway Working," electricity
was used for signalling trains on the cable railway
between Minories and Blackwall. The instruments
used were a form of needle instrument; but the
character of the signalling was different to that on
the Great Western, as would necessarily be the case
RAILWAY SIGNALLING. 5
from the difference in the methods of working the
lines. On the Blackwall railway the signals were
transmitted to the driver of the stationary engine
at either of the termini as required, and indicated
to him when the carriages at the opposite terminus,
and at the intermediate stations in turn, were ready
to proceed, or, on the other hand, when circum-
stances rendered it necessary to stop the engine.
The indicator at each of the termini consisted of
six dials, each of which was capable of indicating
two signals—" Ready " and " Stop." The instru-
ment at each of the intermediate stations was
provided with one dial only, having the same indica-
tions ; and both these and the instruments at the
termini were adapted for sending as well as receiving
signals. Thirty wires were provided for this method
of signalling, several of which, however, were spare
wires for use in case of failure of others in use.
Reverting to Mr. Stretton's records, we are told
that Cooke and Wheatstone introduced, in 1841,
independent instruments for the signalling of trains,
which were intended to show the condition of the
line at all times. They also introduced at the same
time an electric bell communication in order to call
attention. This arrangement possessed the most
important distinctive features of electrical apparatus
for train signalling — viz., independent instruments,
distinct apparatus for different purposes, continuous
indications of the condition of the line, and a means
of communicating instructions for the working of
traffic by a pre-arranged code. The instruments of
1841 were lettered "Stop" on the upper left-hand
t) RAILWAY SIGNALLING.
corner, and "Go on" on the right-hand upper
corner. The same inventors introduced a form of
instrument between Norwich and Yarmouth in 1844,
on which this lettering was replaced by " Line
blocked " and " Line clear " respectively.
The Brighton Company is said to have worked a
form of block through the Clayton Tunnel in 1841.
During the winter of 1843-4, signalling of trains by
telegraph messages was carried out on part of the
old Birmingham and Gloucester Railway. Mr. Stretton
quotes the following quaint instance of the signalling,
as taken from the records of the working between
Blackwell and Bromsgrove.
BLACKWELI. TELEGRAPHS : BROMSGROVE REPLIES :
Bristol goods is approaching here Right ; let her come.
Bristol passenger is approaching here .. Keep her back ; goods not here
yet.
Right now ; send her on.
In 1845, the Bristol and Gloucester Railway
Company is said to have worked absolute block
through Wickwar Tunnel by means of electric bells
and a bell code.
In 1846, the Midland Railway Company is said to
have worked absolute block through Thackley, Clay
Cross, and Duffield Tunnels, by the three-wire block,
with needle instruments.
In 1848, the Manchester, Buxton, and Midlands
Junction Railway Company is said to have worked
a three-wire block through all the tunnels between
Ambergate and Rowsley.
In 1849, the Midland Railway Company had the
following code in use between Desford and Bagsworth
on a three-wire block circuit :
RAILWAY SIGNALLING. 7
' To call attention I stroke of bell.
Passenger train approaching here 2 strokes of bell, 2 beats of needle
to left.
Goods train approaching here 3 ditto, 3 ditto.
The West Bridge train 4 ditto, 4 ditto.
On a train leaving either Desford or Bagsworth,
the following signals were given :
To call attention I on bell.
Passenger train leaving 6 ditto, 6 on needle to right.
Goods train leaving 7 ditto, 7 ditto.
West Bridge train 8 ditto, 8 ditto.
On arrival of a train at either end, the signal given
was :
To call attention I on bell.
Passenger train arrived 2 on needle to left.
Goods train arrived 3 ditto.
West Bridge train arrived 4 ditto.
In 1851, the Great Northern Railway Company
are said to have worked absolute block through all
tunnels between King's Cross and Hitchin.
In 1851, the South-Eastern Railway Company
established block working by means of bell signals.
Continuous indicators having the form of miniature
semaphore signals, and worked in a similar way, were
introduced on the opening of the Charing Cross
Railway.
Tyer's first form of block apparatus was brought
out about 1852, and it is worthy of note that this was
the first attempt at automatic signalling. Treadles
were provided at the entrance and exit of the section,
and the passage of a train over these treadles
intimated its approach and exit from the section
.respectively. The automatic arrangement was sub-
8 RAILWAY SIGNALLING.
sequently abandoned, and was replaced by hand
signalling. The indications provided in this apparatus-
— as in Bartholomew's, which was introduced at about
the same period — were two in number : " Train on
line " and " Line clear." The lettering on Bartholo-
mew's instrument was " Clear," " Closed."
In 1853, Mr. Edwin Clark adapted the double-needle
speaking instrument, in combination with a separate
bell communication, to train signalling on the London
and North-Western Railway Company's line, using
one needle as an indicator for the up line, and the
other for the down line. The two instruments,
although in one case, were quite independent, were
worked by separate wires, and were arranged to give
continuous indications by means of continuous currents?
the handles of the instruments being pegged over
constantly in either one or the other of the two
positions provided. Each dial indicated three posi-
tions, thus : upper part of needle deflected to left,
"Train on line"; upper part of needle deflected to
right, "Line clear"; needle vertical, "Line blocked."
This system was, in so far as the instruments, their
lettering, and the method of using them is concerned,,
substantially the same as any of the three-wire single-
needle systems in use at present. Whilst this is the
case, the lettering " Line blocked " had a different
meaning to that given to it at present, and the " Line
clear " indication was also of a different character..
As an adjunct to the apparatus as already described,,
it is stated that "the telegraph wires were brought
down the posts, so that in case of the breakdown of a
train the driver or guard could run to a post and cut
RAILWAY SIGNAL
the wire and block one or both lines as necessary.'*
From this extract and the statement that the indica-
tions " Line clear " and " Train on line r> were
maintained by continuous currents, it is evident that
the " Line blocked " indication was an emergency
signal, and not used during normal working. Practi-
cally it partook of the nature of an intimation to the
signalman from outside of something out of the
normal order of working, but not necessarily under
his cognisance, which rendered it expedient to take
further steps to protect the line or lines for which the
indication " Line blocked " was being exhibited.
Hence this system, as with others in which
indicators were provided, recognised only two con-
ditions of the line, but it is worthy of record that
it was a three-wire system in which the continuous
indications were maintained by continuous currents.
In 1862, Mr. W. H. Preece devised his three-wire
system of train signalling, in which he used a
miniature semaphore arm to indicate the condition
of the line at all times. Much interesting information
on the subject of the earlier methods of train signalling
is given in a paper read by Mr. Preece at the meeting,
of the Institution of Civil Engineers on January 13,.
1863 ; and the discussion which ensued, and lasted
four successive meetings, is also of a most interesting
character, since it exhibits the opinions of most of.
those who took a prominent part in the introduction
of electrical signalling on railways. Amongst those
who took part in the discussion are the names of
C. V. Walker, Tyer, Bartholomew, Fleeming Jenkin,,
Captain Huish, and several others ; and, as might be.
10 RAILWAY SIGNALLING.
expected, considerable difference of opinion was
shown.
In this paper, Mr. Preece, after commenting upon
the liability of the various forms of needle instruments
to be reversed by atmospheric disturbances (a very
common occurrence at the period previous to the
introduction of the induced needle), and the disturb-
ances due to earth currents and similar causes — "At
certain times and seasons immense masses of elec-
tricity pass through the crust of the earth from the
equator to the pole, and vice versa, traversing the
telegraph circuits in their course and causing great
annoyance and trouble" — strongly urged the desirability
of assimilating the visible signal for the benefit of
the signalman to that exhibited for the guidance of
the drivers of trains of which the signalman was
charged with the control. He also recognised the
relatively subordinate position occupied by the signal-
man at the sending end of the section ; and his
apparatus was designed with a view to show, in
addition to the semaphore indication, the position of
the signal at the distant station. Curiously enough,
this indication (the position of the signal at the distant
station) is shown, by the illustrations accompanying
the paper, to have been made by a needle.
With respect to the general lines on which the
design of apparatus for train signalling should be
based, the following extract from Mr. Preece's paper
is of some interest :
" Mr. Edwin Clark, M.Inst.C.E., in an interesting
report addressed to the London and North-Western
Railway Company upon improvements in their tele-
RAILWAY SIGNALLING. II
graphic system, remarked : ' The following conditions
should, I think, be insisted upon in any application
of a telegraph to railway purposes :
" ' First. The machinery employed must be of the
most simple and evident description, not liable to
derangement, and easily repaired.
" ' Second. The signals must be simple and few, and
so distinctive that no mistakes can occur.
" ' Third. No dependence must necessarily be placed
on the memory of the person in charge, and the
signals should be permanent and not temporary, or
liable to misconstruction or neglect from the absence
of the attendant.
" ' Lastly, and more particularly, no accident should
be actually caused by the derangement of the appa-
ratus or the absence of the signalman, but such
absence or derangement should merely cause
delay.' "
Much interesting information was elicited during
the discussion on Mr. Preece's paper; and it was
stated that Mr. C. V. Walker had used a form of
indicator for a short time on the South-Eastern
Railway, in 1854, m which the indication was given
by the position of a small semaphore arm attached
to the axis of an ordinary needle instrument, one
of the two indications being maintained by a con-
tinuous current.
The inventor of the form of semaphore indicator
and bell combined (Mr. C. V. Walker, F.R.S.) used
on the South-Eastern Railway contributed a series
of articles, entitled " Train Signalling in Theory and
Practice," to the Popular Science Review, which were
12 RAILWAY SIGNALLING.
subsequently extracted by the English Mechanic. In
these articles, Mr. Walker described in most minute
detail the various operations involved in the system
of bell signalling in use, under his supervision, on
the South-Eastern Railway. As the articles afford
a most interesting glimpse of the line of reasoning
on which the pioneers of the block system based their
conception of the requirements of railway signalling,
the following extracts are taken from the issues of
the English Mechanic for July 6 and 20, 1866 :
" In order to illustrate the laws of train signalling,
it will be better to take the simple case of a railway
like the Ramsgate- Margate, for instance, having two
pairs of rails, an up line and a down line, with a signal
station at each end, but no intermediate station. The
fundamental law is — ' Two trains or engines are not to
be allowed to run on the same line, between two signal
stations at the same time.' In order to carry out this
important regulation, upon which the security of those
who travel so largely depends, ' every train or engine
must be signalled out to the next station, before it
leaves or passes a station.' So that when the business
of the day, for instance, commences, station B knows
that train No. i is asking permission to come to him
from station A ; and, to prevent all misunderstanding,
' the train or engine must not be started, or allowed to
pass, until the next station has taken the out signal/
It is not enough for the first station to give the signal,
the other station must take it ; for ' no signal given by
one station is complete until taken by the other station
repeating it,' by which process a clear understanding
is established between the signallers, that the precise
RAILWAY SIGNALLING. 13
signal sent by one is received by the other. The next
rule applicable is that ' every train or engine that
arrives at or passes a station is to be immediately
signalled in to the last station ' ; and it follows, from
what has been already stated, that * no second train
or engine is to be allowed to follow until the in or
arrival signal of the previous train has been taken ' —
that is to say, has been repeated back blow for blow.
" And in order that there may be no mistake as to
whether or not the whole of the train is safely in, it
is not to be signalled as in until 'after it has been
clearly ascertained by actually seeing the tail lamps,
or communication with the guards, that no portion of
the train from any cause has been left behind.'
" Next in simplicity to a signal-box at either end
of a line with two pairs of rails, is that of an inter-
mediate station on a similar line. In this case the
signal-box is provided with a pair of bells of different
tones, or a bell and a gong or steel spiral. They are
placed on either side of the box, each being at the
side nearest to the station with which it is in com-
munication. . . . The rules already given are equally
. in force here, and are carried out precisely in the
manner described. ... On the day of the Foresters'
fete (August 19, 1862) no less than 535 trains were
signalled at one intermediate station in the London
Bridge yard on one pair of bells from early morning
till late at night, all signals also being booked.
" There is a rule essential to intermediate stations,
but, of course, not required at a terminus, that the
•* out signals of passing trains are to be made as they
approach, in order to let them pass without check
14 RAILWAY SIGNALLING.
if the line is clear,' because, unless the out signal, as
we have already stated, be replied to — that is, unless
the out signal, which means ' May I send the train,'
be repeated back, which means ' You may send the
train,' it would have to be checked; for, under such
circumstances, from whatever cause arising, ' the train
must be brought to a stand, and the driver cautioned
to keep a good look-out, because he is running by
sight and fixed signals, and not by telegraph signals.'
" I have heretofore confined myself to the code
which is established for the simplest case of train
signalling, and which is applicable and is applied to
and in force on five-sixths of the railway in question ;
and before passing on to give one or two illustrations
of special codes provided for mixed traffic, which
requires distinctive signals, I may here give certain
constant signals that are universal in their application,
and may always have the same meaning. When a
bell is struck five times, it indicates that the line is
blocked, and that nothing must be allowed to come
on until a signal has been given that the line is clear
again, which latter signal consists of three blows given
and taken twice. The telegraph inspectors give sign
of their presence and test the condition of the
apparatus by exchanging six blows, and an erroneous
signal is cancelled by seven blows.
" The simplest case of deviation from ' a general
code' of signals is when the trains of two companies
travel on the same lines, as jthe South-Eastern and
the Brighton trains between London and Redhill.
In this case one blow indicates a South-Eastern train,
whether up or down, and two blows, a Brighton train ;
RAILWAY SIGNALLING. 15
all other signals remaining unchanged. Or, to take a
case somewhat more complex, and which is the oldest
of the codes, dating as far back as October 29, 1851,
and provided originally for up trains on the half-mile of
line intervening between Spa-road and the entrance
to the joint station at London Bridge — one blow for
a Croydon train, two for a Brighton train, three for a
South-Eastern train.
" It has been further thought advisable, especially
where the trains up and down are very many in
number, that the signalman should be reminded by
some signal visible to the eye that he has given or
taken a certain bell signal ; and this visible signal is
further turned to account by being used in combina-
tion with the audible signal, and thus diminishing the
number of sounds necessary for carrying on traffic.
The visible signals at a glance show the actual state
of the line, whether a train is coming on or not,
whether a train is still going on or is safely in ; in
fact, whether the lines in either direction are free
of trains or not.
11 The Charing Cross Railway, where a system of
this kind has been in full operation since the opening,
will give a very perfect illustration of the joint service
of the eye and ear in interpreting what the hand has
given.
" The -illustration shows the manner in which the
signal-box at Waterloo is fitted up. This box is
intermediate between Belvedere - road and Black-
friars. At the front of the box, in the right and
left hand corners respectively, are placed a bell and
an " electromagnetic telegraph semaphore." Exter-
l6 RAILWAY SIGNALLING.
nally, this instrument presents to the eye a signal-
post on a small scale, similar to those in use on the
railway in question, with a red arm on the left side
:and a white arm on the right side, in like position
with those on an actual signal-post, and capable of
being worked by an electric current up, indicating danger,
•or down, indicating caution, as required ; and the
regulations for working them are such that the arms
at all times indicate the state of the line. Looking
• towards a semaphore, whether actual or electromag-
netic, the red and left arm has reference to trains
receding, the white and right arm to trains approach-
ing; and when an arm is up it indicates that a train
is on the line, and when down that a train is not on
the line. So that, looking at the position of the arms
as they stand in the page engraving, it is evident that
no train is going from Waterloo to Belvedere, and no
train is coming from Belvedere to Waterloo ; both
lines on this side of Waterloo are clear. On the
other side, there is no train going from Waterloo to
Blackfriars, but a train is on its way from Blackfriars
to Waterloo. These semaphore instruments are con-
nected up in pairs — the one on the right-hand side
of the signal-box is connected with its companion
at Blackfriars and works in sympathy with it, the
arrangement being that 'the red arm at one station
and the white arm at the other station work up and
• down together. When the red arm at one station is
up the white arm at the other station is up also ;
when the one is down the other is down.' If an
observer were at Blackfriars he would find the com-
panion semaphore in question on the left side of the
RAILWAY SIGNALLING. 17
box there and labelled Waterloo, and would see the
left — the red arm — up in sympathy with the white,
the right arm of the semaphore in the engraving, and
the white arm down in sympathy with the red or left
arm in the engraving ; and the signalman at Black-
friars would make no attempt to signal on another
up train until the red arm at his station had been put
down by Waterloo.
" The principle upon which the electromagnetic
semaphores are here connected up and arranged is
that ' each station can put the white arm only at
his own station, and the red arm only at the other
station, up or down.' No signalman in this arrange-
ment, which may be varied to meet other cases, has
power to alter the position of his own red arm ; it is
put up behind a train by the next station, and put
down when the train is at that station.
" It will be convenient here in explanation of the
manner of working these instruments to describe the
whole process of signalling a train by bell and
semaphore, and we can then pass on to the description
of the electrical arrangements that are employed
for bringing about the result.
" ' The ordinary position of the arms of the electro-
magnetic telegraph semaphores will be down,' that
is to say, when the line is all clear of trains and
business begins, say in early morning, all the arms
will be down, indicating that no train is moving
When the first train is ready to depart, say from Charing
Cross, the signalman will give the proper bell signal
to Belvedere on the bell, two, three, or four blows,
according as the train is for Greenwich, for the
2
l8 RAILWAY SIGNALLING.
North-Kent, or Mid-Kent, or the main line, and the
Belvedere man will acknowledge this by one blow on
the bell in reply, and without raising the Charing Cross
red or left arm ; this is the signal that the train may go
on, and when the train has passed so that the Charing
Cross man can see the tail lights he gives the out
signal a second time, which the Belvedere man
acknowledges, at the same time raising the red arm
at Charing Cross behind the train, and so protecting
it until it has passed him at Belvedere, when he
signals to that effect to Charing Cross, at the same
time pulling down the red arm there as an indication
that the line is again clear. While these operations
are going on for down trains, others precisely similar,
but in the reverse direction, are going on for up
trains. The separate functions, as well as the com-
bined office of the bell and semaphore, will thus be
readily appreciated. The bell, the basis, as we have
said, of all the mere sound systems, as heretofore
speaks to the ear, and asks not only if a train may
come, but defines the particular kind of train that
is ready to come, and it also tells at the proper time
that the train is in. The semaphore arm has two
motions and communicates alternately, and puts on
record two facts only, and most important facts they
are — either that a train is on the line, or that a train
is not on the line ; and as either one or the other
of these things must always be the case, it is a
standing record at any and at all times of the actual
state of the line, and is of very great service to the
signalman in regulating the enormous traffic with
which he has to deal. The combined office of the
RAILWAY SIGNALLING. IQ
bell and semaphore is now evident. It is not enough,
as we have seen, that the arm of the semaphore
indicates the line clear ; before a train is allowed
to go, ideas must be interchanged by bell signal, and
if the reply is combined with still displaying the
all-clear signal — that is, the red arm down — the train
may proceed. Nor is this enough, for it would be
a contradiction after the train had passed, and is
therefore on a certain length of rail, for the all-clear
signal to remain displayed ; and hence it is that a
second interchange of out bell signals is made, this
time indicating that the train has come on as allowed,
and the reply in recognition of this is combined with
raising the red arm behind the train and retaining it
there until the train is safely in. It is then lowered
without any further interchange of signals, and so on.
It takes far longer to describe these operations than
to perform them. The bell semaphore signal is the
result of a single act — one and the same pressure
on the key sends the bell signal and raises or depresses
the semaphore arm as the case may require, a single
telegraph wire only being required for the combined
system as for the more simple bell system."
Careful consideration of -the records available show
clearly the gradual growth in the number of applica-
tions of electricity from the time of its introduction by
Cooke and Wheatstone in 1839; an(^ also, incidentally,
some of the disadvantages attendant upon isolated
effort, without knowledge of the results obtained and
methods employed by previous workers in the same
iield.
In Cooke and Wheatstone's adaptation of the
2*
20 RAILWAY SIGNALLING.
telegraph (which must have been immediately on its
completion, as it is recorded elsewhere that the
telegraph wires were laid from Paddington to West
Drayton only in September, 1839) to train signal-
ling, the fundamental principle of the existing block
system — the space limit — is imposed, but no special
apparatus is provided for the purpose ; and there
existed no permanent indication of the actual con-
dition of the line other than that afforded by a
comparison of the times at which messages were
despatched and received. Two years later the same
inventors provided instruments of a distinct character
for train signalling alone ; and these instruments were
not only adapted for communication between different
points, but were capable of indicating the condition of
the line. In these instruments, and in those fixed by
the same inventors between Norwich and Yarmouth
in 1844, only two conditions of the line are recog-
nised. To Cooke and Wheatstone belongs the honour
of having originated the present system of train
signalling ; and, from the fact that they employed
independent instruments for indicating the condition
of the line to those used for intimating the require-
ments at various times, they certainly seemed to have
gauged the requirements to a greater degree of perfec-
tion at this early date than some of the later workers
in this field.
It must, however, be pointed out that Cooke and
Wheatstone' s system did not in all respects corre-
spond to the present methods of signalling. As used
between Norwich and Yarmouth as late as 1844, the
instruments did not break up the line into separate
RAILWAY SIGNALLING. 21
and distinct (as far as the signalling instruments are
concerned) portions as is done at present.
In the paper read by Mr. Preece before the Institu-
tion of Civil Engineers in 1863, he says of this system :
" But each station contained as many needles as there
were stations (five in all) on the line, and thus the
position and the progress of every train could be seen
at any moment." We are also told in the same paper
that the system was ultimately abandoned on account
of the difficulty in maintaining the large number of
wires required to work it.
Cooke and Wheatstone's system apparently aimed
at much more than is comprised in the present method
of block working, in that they proposed to show the
progress of a train throughout the whole of the line at
all the signal stations. Such a method as this would
be unworkable at the present day for other reasons
than the maintenance of the wires, although that
would be a much greater item now than then, owing
to the much shorter sections in use.
The method of signalling adopted by the Birming-
ham and Gloucester Railway Company, at the
instance of Mr. McConnell, in 1843, was a distinct
reversion to the method adopted by Cooke and
Wheatstone in 1839. The code of signalling used
by the Midland Company between Desford and
Bagsworth gives no indication of the use of the
instruments as indicators. At the same time, it is
not probable that they were intended solely for the
purpose of train description, which was adequately
provided for by the bell signals. In this code we
find evidence of the recognition of the necessity for
22 RAILWAY SIGNALLING.
preparing the line before the actual arrival of the
train at the entrance to the section protected by
block working. One important feature of the system
is supplied by Mr. Stretton, in the letter referred to,,
which is that the outdoor mechanical signals were
always kept at danger, except when used to indicate
to the driver of an approaching train that the line
was in order for him to proceed.
It is somewhat difficult to decide in how far some
of the systems of signalling referred to are entitled
to the name of " block" systems as the term is
understood now. The absence of the codes in many
cases, and the regulations for the guidance of those
entrusted with the work, makes comparison with
present-day methods difficult. There is some reason
to doubt whether the systems did, in particular
instances, impose a space limit ; and it also appears
that in some instances after trial of the space limit,,
it was abandoned on account of the delay caused
by the sections being too long.
Thus, speaking of the system in use on the London
and North-Western Railway in 1853, and much later,
Mr. Preece, in the paper referred to, says : " It must
be observed that in working this system on the
London and North-Western Railway, that company
do not strictly adhere to what is termed the block
system. They allow two, three, and sometimes four
trains to be on the same length at the same time.
The signal ' Train on line ' is simply received as
a cautionary signal."
The system of bell signalling brought into use on
the South-Eastern Railway in 1851 was to all intents
RAILWAY SIGNALLING. 23
and purposes a block system, as is shown by the
extracts from Mr. Walker's articles. Whilst no
indicators were provided originally for showing the
condition of the line at any stage of the operations,
the rules under which the system was worked were
such as to ensure perfect safety, if invariably observed.
This is all that can be said of any of the systems in
use at present.
A study of the rules under which the South-Eastern
system was worked shows how fully the requirements
had been reasoned out and met so far as was possible
by a purely aural system of signalling. The absence
of continuous indications of the condition of the line
was an undoubted defect, in that it relied too much
upon the signalman's memory and attention to his
train-book entries. The introduction of the electro-
magnetic telegraph semaphore remedied this defect,
but a closer study of the articles will show that the
instrument did not afford an indication for what Mr.
Walker considered an important point — the exchange
of signals preliminary to the entrance of a train into
the section.
It is not necessary to follow all the different methods
of signalling for which the title of " block " is claimed.
In many instances the title, as at present understood,
is not justified. Even where needle instruments were
used, the signals in many instances were mere momen-
tary deflections of the needle, intimating in one case
the entrance, and in another case the exit, of trains
from the section of the line over which the com-
munication extended.
Speaking of the system of signalling in use on the
24 RAILWAY SIGNALLING.
Great Northern Railway, Mr. Preece, in the paper
so often referred to already, characterises it as a
system that was understood by no one but themselves.
Referring to the system used by the Brighton Company
between the ends of Clayton Tunnel, he states that
the signals are momentary deflections of the needle ;
and he cites an instance where the system broke down
and led to an accident of some magnitude.
Enough has probably been said on this point, how-
ever. Whilst instances of earlier methods of working
are of some interest and value in enabling us to trace
the growth and general line of progress, they are
not, for the purpose under consideration, of so much
value in indicating the lines of progress from present-
day methods, except in the most general sense, on
account of the great changes that have been made
in railway management as a whole ; and also on
account of the immense increase in the volume and
variety of traffic to be dealt with, and the greater
importance for its speedy transit.
Of the advantages obtained and the safety ensured
by the system of block signalling of trains, of which
the foregoing are examples of the initiatory work, it
is not necessary to speak. The extraordinary develop-
ment of the habit of travel during the last thirty years,
the necessity for the quick transit of imported food-
stuffs to and from the centres of distribution, together
with the immense growth of trade, rendered the
adoption of some method of safe control not only
expedient but necessary. How successful the block
system has been in effecting these objects may be best
seen by comparing the number of accidents for a given
RAILWAY SIGNALLING. 25
quantity of traffic in two equal periods before and
after its establishment. At the same time it must be
admitted that occasions do occur where, owing to no
defect in the system itself, but on account of causes
which cannot always be foreseen, accidents, involving
loss of life or limbs, and considerable destruction of
property do occur. Under the rigorous enquiries to
which these accidents, and the events leading to them,
are subjected by the Board of Trade officials, it is
usually found that the occurrence is due to some lapse
on the part of the individual entrusted with the
working of the apparatus. Not only is this the case
with the more serious accidents, but also with those
which, whilst the result of an infraction of the rules
of the service, have not had such consequences as to
call general attention to them. Hence, we find that
the reports of the inspectors of the Board of Trade
teem with suggestions and recommendations, the
ultimate object of which is control of the controller.
The block system owes its inception to the recognition
of this necessity ; and the various stages of its progress,
from its earliest form to the present period, has been
rendered necessary in consequence of the liability of
the human machine to break down at critical or
inopportune moments.
In his pamphlet entitled " Telegraphic Railways,"
published in 1842, Sir W. F. Cooke says:
"It may be considered that the maximum degree
of safety and efficiency attainable by subsidiary regu-
lations is already secured on the great double lines
of railway," and that "to the comparatively high
degree of safety now attained (1842) in railway
26 RAILWAY SIGNALLING.
travelling, depending then, as I have said, upon
vigilance and punctuality in the conduct of the
trains, it is proposed to superadd a physical cer-
tainty of their relative places on the line at any
moment."
Even now, fifty-five years after these words were
written, and with the aid of appliances not then con-
ceived of, and with rigid codes and equally rigid
regulations not then considered necessary, it is not
too much to say that they are the words of an
optimist whose aspirations have only partially been
fulfilled.
CHAPTER II.
Object of Apparatus. — The principal object aimed;
at by the use of all the complex apparatus employed
in signalling the passage and controlling the move-
ments of trains, in their due order of importance, is
safety. A second object of only slightly less import-
ance at the present day, is the speedy transference of
passengers and goods to their respective destinations.
Both these objects are promoted by the system of
signalling to which the general name of "block" is
almost invariably applied in this country. The safety
of traffic is promoted by the preservation of a space
between successive trains on the same line of rails.
The speedy transfer of traffic from point to point is
promoted by the use of regulations which direct
what shall be done under almost all conceivable
conditions, and by careful arrangements of traffic in
accordance with the fixed regulations.
The space provided between successive trains is not
uniform on all lines, nor is it uniform throughout
the lines of any one company, neither is the space
so preserved always constant over the same division
of the line. Consideration will show that there is no
necessity for either uniformity or constancy. If a
space can be ensured between one train and the
preceding or following train, the magnitude of the
space is immaterial. Theoretically this position is
unassailable ; and so long as work is carried out in.
UNIVERSITY
Or r
28 RAILWAY SIGNALLING.
the spirit in which the system is conceived, no
mischievous effects can or will be felt.
The term " block " is frequently applied to the
electrical portion of the apparatus used only ; and
it is rather too often assumed that this form of
signalling is the be-all and end-all of railway working.
Whilst too much importance cannot be given to the
due performance of the duties entailed by electrical
signalling, it should not be forgotten that it is simply
a means to an end, and not the end itself; and that
there are other forms of apparatus which play an
equally important part, and are equally as indispensable
for the safe and speedy working of traffic.
Classification. — Railway signalling may be divided
into distinct classes :
(a) The electrical part, by which arrangements for,
and notification of, the passage of traffic are made ;
and
(b) The fixed signals, by which the actual move-
ments of trains are controlled.
Both classes of signals are operated by the same
person ; the location of the cabins or boxes (in which
the apparatus is placed), which determines the lengths
of the sections into which the line is split, being fixed
in accordance with local conditions or considerations
connected with the volume of traffic. Where traffic
is light and junctions are not numerous, the length
of a block section may be several miles. On the other
hand, if junctions are numerous and traffic heavy,
or if special conditions have to be taken into account,
vthe length of sections may be only two or three
RAILWAY SIGNALLING. 2Q
hundred yards; and a cabin and its outdoor signals
may be within sight of the next one or two cabins
in either direction. The shorter length of sections
naturally facilitates traffic, more especially if the line
is fed from one or other of those points.
With reference more particularly to ordinary double
lines of railway, it may be said that there are two
methods of working, both of which are designated as
"block" systems. One of these may be termed a
positive block; the other is a negative one. In the
first the length of line comprising any section is always
considered as blocked against traffic, until permission
has been asked and given for a train to enter at the
sending end. With the second, or negative system,
the line is considered as clear for the entrance of a
train as soon as, and at any time after, the previous
train has been signalled as clear from the advance end
of the section. The second system is in use on only
very few and comparatively unimportant lines. All
the larger lines have adopted the absolute block, or
positive system of working.
Responsibility. — The responsibility for correct
working on the absolute system is not, for any one
line of rails, equally divided between the signalmen
controlling the section. Since the signalman at the
sending end must ask, and receive permission, before
allowing a train to proceed to the cabin in advance,
his responsibility is necessarily less than that of the
signalman who, by according such permission, assures
him that the line is clear o previous traffic. Under
such circumstances the signalman at the entrance to
a section becomes, practically, a look-out man, more
3O RAILWAY SIGNALLING.
advantageously situated in respect to the direction
from which trains may be expected, for the actual
controller of that line of rail, and confines himself,
generally, to acting upon the instructions received
from his confrere. This rule, like most others, is not
without its exception, and there are occasions, as will
be seen, when the signalman at the entrance of a
section transmits a definite order, for certain purposes,
to the signalman at the exit of the section. The
responsibility for the whole of the traffic through any
section is, of course, fairly averaged, since the cabin
which marks the entrance to the section for down-
line trains, also marks the exit of the same section for
up-line trains.
Whilst this is the case with regard to the signalling
previous to the entrance of a train, the responsibility
of the signalman at the sending end is the greatest
for the exhibition of the correct outdoor signals for
the guidance of the drivers of trains ; and this respon-
sibility is, theoretically at least, equally great whether
the section is occupied or not. Any neglect or mistake
on the part of the sending signalman, in allowing
trains to pass without the requisite permission from
the other end, is liable to produce consequences
equally as serious as those which would result from
a mistake on the part of the receiving signalman, in
accepting a train before the previous one was clear
of the section, and under the protection of his signals.
Practically speaking, there is not the slightest
difference between the two cases, except that they
are made in working different classes of signals.
Very slight consideration will show that responsi-
RAILWAY SIGNALLING. 31
bility does not rest with the signalman alone. It is
equally as important that drivers of trains should be
as accurate in their interpretation of the signals
exhibited for their guidance. Any misapprehension or
carelessness on the part of a driver is calculated to
produce results equally as disastrous as any that can
ensue from the mistakes of the signalmen ; and the
chance of minimising the consequences by subsequent
action are less, since they have lost their only means
of control over the driver and his train. Since drivers
must necessarily depend largely for their efficiency
upon, at least, one of their physical powers being of
the highest possible class, railway companies rightly
insist upon drivers and firemen being possessed of
the most perfect vision. The importance of good
eyesight to drivers and firemen cannot be over-
rated. It is necessary that they shall be able not
only to see the positions of signals at some distance
ahead, but they must also be able to distinguish
the signal relating to themselves from amongst a
number of others, in similar positions, at points
where signals are numerous. Over and above this
is the necessity for picking up the various signals
on a long run, in regular rotation, in order that the
driver may localise his position when circumstances
prevent him from noting familiar landmarks as he
passes. During foggy weather this is a most important
desideratum, and under any circumstances accurate
localisation enables the driver to distinguish his signal
with greater facility, on account of his knowing exactly
where to look for it, and adds to the comfort of his
position.
32 RAILWAY SIGNALLING.
Hence we see that, considered as a whole, the
responsibility for such accidents as are due to
infraction of the signalling rules is fairly evenly
divided amongst the three persons actively engaged
in the working of traffic. All have, at one time or
other, contributed their quota to the chapter of
accidents : the first line of defence has been broken
by the receiving signalman accepting a second train
when the first was in the section ; the second line has
been broken by the signalman at the sending end
allowing trains to enter the section without first
obtaining the necessary permission ; and the third line
of defence has been broken also by engine-drivers
running past signals at danger ; and it must by no
means be considered that those cases which have
received prominent attention in consequence of the
results following them are the only cases that occur.
Besides the possibilities of accident due to incorrect
signalling, accidents are liable to occur from other
causes. Malicious attempts to derail trains — for-
tunately, generally unsuccessful — are not altogether
unknown. Accidents are sometimes due to hidden
and unsuspected defects in the permanent way, in
the locomotive, or in some of the rolling-stock ;
trains become divided occasionally from various
causes ; vehicles run away in the right direction for
the line they are on, or in the wrong direction, as
the case may be and the gradient serves. Accidents
due to such causes as these, and others of a similar
character, may take place anywhere on the line. If
they do not foul the other line, and block rules are
followed, nothing further occurs beyond the con-
RAILWAY SIGNALLING. 33
sequences due to the accident itself. If the other
line is fouled, the accident may be doubled by a train
on the other line running into that to which a mishap
has already occurred. Such possibilities as these call
for the utmost vigilance, promptitude, care, and nerve
on the part of the drivers of trains ; and the necessity
is not lessened by the occurrence of such cases being
comparatively rare. The heavy responsibility attached
to the position of an engine-driver in this and other
respects justifies railway companies in imposing the
most rigorous tests, in order to ensure the highest
qualities in this class of their service ; and at the
same time stamps the driver with a hall-mark which
it should be his greatest pride to maintain.
Analysis of Block Signals.— The electrical signals
used in the working of traffic on the absolute block
system are, in all cases, of two kinds : (a) Those
which are of a permanent character, and indicate, in
accordance with the conventions under which the
instruments are used, the condition of the line more
or less completely. (6) Those which are transient only,
and which are intended to convey information upon
which subsequent actions are to be based. The latter
signals are invariably made by a bell code, or a combi-
nation of bell and dial signals where the needle form
of instrument is in use ; the former are made by
instruments which are capable of exhibiting continuous
indications of different characters. There are not many
varieties of the instruments used for this purpose ;
most of them convey their information by the position
of a needle in accordance with the lettering of its
dial, or by the relative position of a miniature sema-
3
34 RAILWAY SIGNALLING.
phore arm. Whilst this is the case with the form
of indicator, the variety of methods employed to pro-
duce the required results is very great, each instrument,
no doubt, being characteristic of its designer's opinion
of the best method to be employed.
REGULATIONS FOR TRAIN SIGNALLING BY BLOCK
TELEGRAPH SYSTEM.
Number of Beats of
BELL SIGNALS. the Bell.
To call attention I
Train on line 2
(Double the usual
pause bet ween the
Be ready for an ordinary goods, mineral, ballast
train, or light engine
beats must be
given for trains
which have to
stop to work in
the section. )
Be ready for a passenger train 4
Be ready for express goods, fish, cattle, through \
goods, through mineral, through ballast train, or V 5
through engine and van I
Be ready for express London and Scotch goods, "\
meat fish, butter, or yeast train ( •)» I (Double the usual
special butter or yeast tram ( .-)'. or break-. T pause bet ween the
down van train or engine, sent to assist m case of I f -.
breakdown J
Obstruction danger signal 6
Stop and examine train 7
Signal given in error (cancel signal last sent) 8
Train passed without tail lamp 9
Train divided 10
Shunt train for following train to pass n
Vehicles running back on wrong line 12
Section clear and station or junction blocked 13
Vehicles running away on right line 14
Opening of signal cabin 15
Testing 16
Closing of signal cabin 17
Time signal 18
RAILWAY SIGNALLING. 35
Number of Beats of the
DIAL SIGNALS. Needle.
'Express or special passenger train On line, 2 left.
• Ordinary or through goods, mineral, ballast) Qn j. ]eft
train, or through engine and van /
Ordinary or excursion passenger train On line, 4 left.
Express goods, fish, or cattle train On line, 5 left.
Express London and Scotch goods, meat, fish, i On line, 5 left.
butter, or yeast train ( ), special < (Double the usual pause
butter or yeast train ( ) ( between the beats.)
-Shunting 6 left.
Light engine On line, I right, 3 left.
Two engines or trains coupled On line, 3 right, 3 left.
Line clear of train or engine 2 right.
•Caution 4 right.
Line clear of shunting 6 right.
.Breakdown van train On line, 5 left, 3 right.
i On line, 5 'eft, 3 right.
Engine sent to assist in case of a breakdown ... < (Double the usual pause
( between the beats.)
Platelayer's lorry entering a tunnel On line, 3 left, 4 right.
•Goods, mineral, or ballast train which has to 1 ^ ,. , f . ,
stop to work in the section f On hne' 3 left> 3 right.
f On line, I right.
OIlo. engine assisting at the rear of a train «g^S5t£
V train assisted.)
1. When the instruments are not in use the handles must be kept
aipright ; the needles will then hang vertically, and when in that
position will indicate "line blocked."
2. When commencing to signal a train, the "call attention" signal
must be the first signal given ; all signals must be acknowledged by
repeating them, and no signal must be considered as understood until
it has been correctly repeated to the sending station. When a signal
is not promptly acknowledged, it must be constantly repeated, except
in the case of the signal "be ready," which must be repeated at short
intervals, and in the case of the signal " section clear and station or
.junction blocked," which is not repeated by the sending cabin.
3. (a) If the line is not clear at the time the signal "be ready"
is received, the signalman must not repeat the signal, or acknowleage it
in any way, until the line is clear, and after having pegged the needle
;to " line clear," the line must not be allowed to be fouled until the
3*
36 RAILWAY SIGNALLING.
train for which the signal " be ready " has been given has been brought
to a stand at or has passed the section home signal.
(b) When the signal " be ready " is offered to an advance cabin whilst
the section is occupied by a train previously signalled, and it is afterwards
found necessary to cancel such signal "be ready," the "signal given
in error (cancel signal last sent)" must not be given until the
signal "line clear," or the signal "section clear and station or
junction blocked " for the first train has been received from the advance
cabin.
SICNALCABIN SICNALCABIN SIGNALCABIN
A. B. C.
^ " " x SIGNAL
CABIN
4. For the purpose of illustrating the course to be adopted, let*A, B,.
and C represent three block signal cabins, and the process of signalling a
train is as follows : On the approach of a train to cabin A, the signalman
will " call attention " of the signalman at cabin B, and then give the
signal "be ready," and the signalman at cabin B, after having, in
accordance with Rule 7, ascertained that the line is clear upon which the
train is to tun, must repeat the signal, and peg the needle to " line clear." '
As soon as the train has passed cabin A, the signalman there must give the
bell signal " train on line," upon which the signalman at cabin B must
acknowledge the signal and unpeg the needle. The signalman at cabin A
must then indicate to the signalman at cabin B the kind of train that is
approaching by giving the proper dial signal, which the signalman at cabin B
must acknowledge by repeating, and having received the intimation that
his acknowledgment is correct, by the signalman at cabin A holding the
needle over to " train on line," he must peg it in that position, and then
" call attention " of, and give the signal " be ready " to, the signalman
at cabin C. As soon as the train has passed cabin B, it must be signalled
in a similar manner to the signalman at cabin C, who must forward the
signal "be ready" to the next cabin, and so on throughout the block.
RAILWAY SIGNALLING. 37
When the train has passed the advance signal at cabin B, and is continuing
its journey in the next section, or has been shunted clear of the main line,
the signalman at cabin B must " call attention " of the signalman at
cabin A, and give the proper signal, indicating that the line is clear of the
train, which must be duly acknowledged by the signalman at cabin A.
When the distance between the home signals at cabins B and C is less than
400 yards, the signalman at cabin B must not, when a passenger train
is signalled, acknowledge the signal "be ready" to the signalman at
cabin A until after he has sent the signal " be ready " to the signalman at
cabin C, and received its acknowledgment, unless special instructions exist
to the contrary.
5. No train must be allowed to pass or start from any station or junction
where the block system is in operation, nor any obstruction of the line be
allowed to take place, without the signals having been previously made
and acknowledged as herein directed.
6. The " danger " signal must always be exhibited at the home,
distant, and advance or starting signals, except when required to be
lowered for a train to pass ; and before any signal is lowered, care must be
taken that the line on which the train is about to run is clear. So long as
the advance section is not clear, the signals must be kept at danger until
the speed of an approaching train has been so reduced as to admit of it
stopping before reaching the home signal : the home signal may then be
lowered to allow the train to draw within it towards the advance signal.
When a light engine, or a train not conveying passengers, arrives at a
cabin before the advance section is clear, and has to be run into an
independent or be sent forward to an advance or starting signal, the
driver must be verbally instructed to proceed to the next cabin with
caution when the advance, starting, or independent signal is lowered.
Where advance or starting signals are not provided, the engine or train
must be brought to a stand at the cabin, and the driver must then l)e
verbally instructed to draw his train fully within the home signal, and to
proceed to the next cabin with caution, as soon as he receives permission
from the signalman, by hand-signal, to go forward. This will be given by
green flag by day, and by green light by night.
7- (a) In dealing with trains of every description, except as provided
for in clauses (b), (d), and (e), the line in the rear section must always be
kept blocked until the preceding train has either been shunted clear of the
main line or has passed the advance signal, and is continuing its journey in
the next section, or, where there is no advance signal, has passed the home
signal at least 400 yards, or the cabin in advance, if within this distance,
and is continuing its journey in the next section.
38 RAILWAY SIGNALLING.
(b) In dealing with light engines or trains not conveying passengers im
clear weather, and under ordinary circumstances, should the signal "be
ready " be offered whilst another train not conveying passengers or a light
engine is standing or shunting within the home signal, or when the line
will be occupied by shunting before the train signalled will arrive, the
" be ready " signal must not be acknowledged, but the signal " section
clear and station or junction blocked" must be given and
acknowledged. The signalman receiving such signal must stop the
approaching train, and verbally instruct the driver to approach the cabin
in advance with caution, informing him why it is necessary to do so, and
then give the bell signal "train on line," upon which the signalman at
the cabin in advance must unpeg the needle, and the sending signalman,
must give the proper dial signal. When the last train dealt with under
this regulation has passed out of the section, the signal " line clear " must
be given and ordinary signalling resumed. When some time is likely to-
elapse before the train for which the signal " be ready " has been sent
is ready to enter the section, the " section clear and station or
junction blocked " signal must not be acknowledged, but when the train,
is ready to enter the section, the signal " be ready " must be again sent,
so as to give the signalman at the cabin in advance an opportunity of
receiving the train under Rule 4. Trains signalled as having to stop to
work in the section must only be accepted under the provisions of the
signal "section clear and station or junction blocked," and the
driver must in all cases be cautioned as herein required.
(c) In reference to all trains approaching junctions, the principle must
be strictly acted upon, except as provided in the next clause of this rule,,
that they must not approach a junction at the same time on sections which
converge to a fouling point, either by running into one line or by crossing
each other to different lines ; and the diagram below is given as an illus-
tration : Whenever a train is signalled as having entered section D, no-
engine or train must be permitted to proceed beyond the junction home
signal on its way from section A to section E, or to enter section P, but
may be permitted to pass from section A to section C ; and whenever a.
RAILWAY SIGNALLING. 39
train has been signalled as having entered section P, no engine or train
must be permitted to enter section D, but may be permitted to pass from
section A to section C, or from section A to section E.
(d) In dealing with trains, neither of which conveys passengers, in
clear weather, and under ordinary circumstances, when approaching a
junction on sections which converge to a fouling point, either by running
into one line or by crossing each other to different lines, the mode of
signalling given in clause (b) of this rule must be adopted. When the
bell signal " train on line " and the proper dial signal have been given
and acknowledged, the needle must be pegged to "train on line."
(e) In dealing with passenger trains which have to connect at a junction
or junction station, if one such train be standing at a junction or junction
station, whilst another is signalled to it, the signalman at the junction or
junction station, as the case may be, must give the signal " section clear
and station or junction blocked," whereupon the signalman at the
rear cabin, after duly acknowledging this signal, must stop the approaching
train and warn the driver to go forward with caution, informing him why
it is necessary to do so, and then give the bell signal "train on line,"
upon which the signalman at the cabin in advance must unpeg the needle,
and the sending signalman must give the proper dial signal ; after receiving
acknowledgment of this, he must note the circumstance in the remark
column of his train register book, and the station signalman must not
give the signal " line clear " until the last train has cleared the section.
Where there is an intermediate cabin between the junction cabin and the
station cabin, this rule will apply as between the intermediate cabin and
the station cabin, and not as between the junction cabin and the inter-
mediate cabin.
8. (a) Should a train or light engine pass a cabin without having a.
"tail lamp" in the rear by day, or the usual signals by night, the
signalman must not give " line clear " to the rear cabin, but at once
give the signal "train passed without tail lamp" to the advance
cabin. This signal having been acknowledged, he must call the attention
of the rear cabin, and on gaining attention, must give the signal "caution,"
and, after acknowledgment, peg the needle over to "train on line";
the rear cabin signalman will thereupon stop any train following, and
verbally instruct the driver to proceed cautiously towards the cabin in
advance, informing him why it is necessary that he should do so ; the
signalman must then give the bell signal " train on line," upon which
the signalman at the cabin in advance must unpeg the needle, and the
sending signalman must give the proper dial signal. As soon as the train,
the driver of which has been cautioned, has passed the cabin from whence
40 RAILWAY SIGNALLING.
the signal "caution" was received, the signalman there will recommence
signalling in the ordinary manner.
(b) Should a light engine pass out of a section when the signal for a
train has been received, the signal "stop and examine train" must be
given, and the same precautions taken as set forth in the preceding para-
graph ; and the signal " stop and examine train " is also to be used
in the event of a signalman observing anything unusual on a train passing
his cabin which might cause an accident. Any signalman receiving such
signal must immediately exhibit the danger signals, to stop any train coming
from or going towards the cabin from which the signal was received. The
train, when stopped in obedience to the signal " stop and examine
train," must be carefully examined, and dealt with as occasion may
require. Should any train going in the opposite direction have been
stopped, it must be allowed to proceed after satisfactory evidence has been
obtained that the line on which it is about to run has not been obstructed.
Where practicable, and speaking instruments or telephones are provided,
the signalman must also advise the cabin in advance the cause of sending
the signal "stop and examine train."
(c) If a signalman has reason to suppose that a train which has arrived
at or passed his cabin has left any portion of the train on the line, he
must, in addition to carrying out the instructions with respect to the line
on which the train is running, stop the first train that arrives on the other
line, inform the driver what has occurred, and instruct him to proceed
-cautiously lest any portion of the train which has broken loose has fouled
the line on which he is running ; and the same precaution must be taken
as to stopping a train on the other line whenever any train which has
been signalled " on line " is unusually long in passing through a section.
, 9. The " obstruction danger " signal must be given to the cabin in
the rear whenever, after permission has been given for a train to approach,
it is necessary, owing to an unexpected obstruction of the line, that the
train should be stopped at the cabin in the rear. The signalman, on
receiving this signal, must at once place his signals at " danger," put
detonators on the rails, and exhibit the hand danger signals to stop the
train ; after the train has been brought to a stand, he must give the bell
signal "signal given in error," and not allow the train to proceed
until the signals have again been given and acknowledged.
10. "Train Divided." — The "train divided" signal is only to be
used in the event of a signalman observing that a train has become divided,
and is running in two or more parts. The signalman receiving the signal
must stop any train travelling in the opposite direction ; and if the divided
irain is running on a falling gradient, where the stoppage of the first part
RAILWAY SIGNALLING. 4!
would risk a collision by the second part overtaking it, the signalman, if
the line be clear ahead, must not exhibit the danger signal to stop the first
portion, but must give the driver a green signal, either by flag or hand-
lamp, waving such signal slowly from side to side, and endeavour to advise
him of the circumstances as he passes ; but if the line be not clear ahead,
or if the train is running on a rising gradient, or where the line is level,
the signalman must stop the first portion and deal with it as expeditiously
as possible to prevent the second portion coming into collision with it.
Should any train going in the opposite direction have been stopped, it
must not be allowed to proceed until satisfactory evidence has been
obtained that the line on which it is about to run is not obstructed.
11. (a) "Vehicles Running Back on Wrong Line."— Should any
vehicle or portion of a train be running back in the wrong direction, the
signalman must call the attention of the signalman at the next cabin
towards which the vehicle or portion of a train may be running, by giving
the signal " vehicles running back on wrong line." The signalman
receiving this signal must immediately exhibit the danger signals, to stop
any train coming from or going towards the cabin from which the signal
was received, and take any other protective measures that may be
necessary, such as turning the runaway vehicles across to the other line,
or into a siding, as may be most expedient under the circumstances.
In the event of vehicles being turned across to the other line, the signal
" vehicles running away on right line " must be passed on to the
next cabin.
(b) The signalman sending the signal must stop any train on the other
line, tell the driver and guard what has occurred, and, when the proper
signals have been given and acknowledged, instruct the driver to proceed
cautiously.
(c) On single lines, vehicles running towards the station or cabin where
the train staff is, must be considered running back on the wrong line,
and treated accordingly.
12. (a) "Vehicles Running Away on Right Line."— If any vehicle
or portion of a train has escaped, and is running away in the proper
direction on the right line, the signalman at the cabin in advance must
be advised of the fact by the signalman at the cabin in the rear giving
the signal " vehicles running away on right line." The signalman
forwarding this signal must immediately exhibit the danger signals, to
stop any train coming from or going to the cabin towards which the
vehicle or portion of train is running ; and the signalman receiving this
signal must immediately exhibit the danger signals, to stop any train coming
from or going towards the cabin from which the signal was received, unless
42 RAILWAY SIGNALLING.
there is a train in block in the same section as the runaway vehicle and in
front thereof, in which case, if the line is clear, such train must be allowed
to pass before the signals are exhibited to stop any train coming from the
cabin in the rear. The signalman must arrange for the line on which the
vehicles are running to be cleared, and, if necessary, send the signal
forward, and take such other measures as he may consider expedient under
the circumstances.
(b) On single lines, vehicles running away from a station or cabin where
the train staff is, must be considered as running away on the right line, and
dealt with accordingly.
13. (a) Before shunting a train from one main line to another, or
obstructing the line by shunting operations, the signalman at whose cabin
the shunting has to be done must give the •• call attention " signal and
then the dial signal " shunting," and, after acknowledgment, the signal-
man at the receiving cabin must hold the needle to *' train on line," in
which position the signalman at the sending cabin must peg and keep it
until the shunting is over and the line clear, when he must give the signal
"line clear of shunting," and receive its acknowledgment.
(b) When the shunting is being done within the home signal, the signals
for an engine or train not conveying passengers may be accepted under
clause (l>) of Rule 7. It will not then be necessary to give the signal " line
clear of shunting " to the cabin in the rear.
(r) Trains or engines approaching a junction on a line converging to a
fouling point, or when leaving a siding to proceed on their journey, or
crossing directly over another running line, are exempted from the
operation of clause (a) of this rule, and must be dealt with under Rule 7,
clauses (c) and (a).
14. If, from any cause, the necessary signals cannot be forwarded and
received, no train must be allowed to pass a cabin and enter upon that
section of the line where the failure exists, without having been previously
brought to a stand, and the driver informed of the circumstance, and how
many minutes the preceding train is in advance. When this has been
done, the driver must be instructed to proceed cautiously to the cabin in
advance, and this rule must be acted upon until the signal communication is
restored. An entry must be made in the Train Register Book of the arrival
and departure of all trains worked in this way.
During the time that block working is temporarily suspended, from any
cause, the number of each engine entering the section must be entered in
the remark column of the Train Register Book. As soon as the signalman
"at either end of the section where the interruption has been, becomes aware
that the instruments are again in order, or that block working may be
RAILWAY SIGNALLING. 43
resumed, he must give the testing signal, which must be acknowledged by
repeating, after which, the needle of the instrument that has been out of
order must be worked quickly from side to side. This signal must be
repeated to show that the instruments at each cabin are in order. The
needle or needles of the instruments must then be pegged to " train on
line." After the needles have been pegged to " train on line," the signal-
man must stop the next train or engine entering the section, and give the
driver an extract, on which must be written " Engine No. — Is the last
one cautioned." The driver must stop at the next cabin then open, and.
hand the extract to the signalman, upon receipt of which the signalman,
must give " line clear " to the rear, and the signalman giving the extract
must not allow another train to enter the section until he has received this-
signal. The signalmen on each side of the defaulting cabin must at once
report the case to the station master, and record it also in his Occurrence
Book.
15. The signalmen, on giving signals, must see that the needles are
firmly and completely pegged over ; and when the needles are pegged
• »ver at the opposite end, they must see that the handles of the instruments,
are perfectly upright. The pegs must not be placed on the handles,,
except when required for the purpose of pegging the needles over. The
needles and bells must not be moved quickly, each movement being made
sl(nuly and distinctly.
1 6. All signals as received and forwarded must be entered, at once, in the
proper column of the train register book. When the exact time is under
half a minute, the half minute is not to be counted ; when half a minute or
more, the time is to be recorded as a minute. Thus, a signal at 30^
minutes must be counted as 30 minutes ; and a signal given at 304 or 30!.
minutes, as 31 minutes.
17. Opening and Closing Signals. — At a signal station or cabia
which is closed during the night, the signalman, on commencing duty in.
the morning, and when going off duty at night, must give the appointed
signals in each direction, and an entry of the time these signals are sent
and acknowledged must be made in the books at each cabin. Any defect
in working must be noted in the Occurrence Book, and at once reported
by the signalman to the station master, who must immediately acquaint
the telegraph lineman of the circumstance.
1 8. Where speaking instruments are provided the signalmen are required
to look for the time telegram, which is sent daily at 10 a.m., and on it&
receipt immediately to send the " time signal " to the advance and rear
cabins where these are unprovided with speaking instruments. The
timepieces to be corrected if necessary.
44 RAILWAY SIGNALLING.
Consideration of the code of signals on page 34 —
which was a re-issue in 1891, but is not now in use —
with the explanatory regulations accompanying it,
shows that a great variety of signals has to be pro-
vided for. The system with which this code was
used is a three-wire needle system, and a study of
the conditions under which the various signals are
applicable suggests a convenient division for purposes
•of analysis.
Confining our attention for the moment to the bell
signals, and leaving out of account the " Call atten-
tion " signal, we find that the third, fourth, fifth,
and sixth signals are all varieties of one and the
same signal, and are intended to intimate a desire
to send different classes of traffic through the section.
These may be called the " preliminary " signals, since
upon the response to them depends the future move-
ment or detention of the train to which they refer.
The title of this signal gives the impression of a
command ; it is, however, really a request, and the
title is not really applicable, for, quoting the regula-
tions respecting the signal, we have " If the line is
not clear at the time the signal 'Be ready' is received,
the signalman must not repeat the signal, or acknowledge
it in any way, until the line is clear."
The bell signal " Train on line " is also a form of
preliminary signal, but it should be classed with the
"Call attention" rather than the "Be ready," since
it is practically a signal by which the sending signal-
man intimates to the man at the advance cabin the
necessity of changing the position of the block
indicator from "Line clear" to "Train on line."
RAILWAY SIGNALLING. 45
The second division of signals may be called
" emergency " signals, and includes all such signals
as are intended to notify departures from the normal
order of working, necessitating exceptional means
being taken to meet the emergencies they represent
in an adequate manner. In this class may be included
the " Obstruction danger signal," " Stop and examine
train," "Train passed without tail lamp," "Train
divided," " Vehicles running back on wrong line,"
•' Vehicles running away on right line," and also
the " Cancel signal last sent " signal.
A further division of the bell signals consists of
such as are required for deviations from ordinary
straight away running of trains, and would include
the " Shunt train for following train to pass," and
"Section clear but station or junction blocked." The
first of these signals is an intimation to the signalman
at the advance end of a section of the approach to
the sending end of a train of a more important
character than that of the train which is occupying
the section ; and this signal is so clear as to have
been ignored in the regulations attached to the code.
The second signal included in this class is an impor-
tant one, on account of the limitations imposed on
its use. It can only be used for trains which do not
convey passengers, and, practically, when advantage
is taken of it, the section is worked at caution. If
the length of a block system is defined as the distance
between the signal controlling the entrance to that
section, and the signal controlling the entrance to
the next section in order, the adoption of such a
rule of working constitutes an infraction of block
46 RAILWAY SIGNALLING.
working where " The object of the system of block
telegraph signalling is to prevent more than one train
being in the section between two block signal cabins
•on the same line at the same time."
The fourth division into which the bell signals may
ibe separated consist of "special" signals for objects
other than the routine work of signalling passing
trains, or marshalling them as may be necessary.
Included in this division are the " Opening of signal
cabin," " Testing," " Closing of signal cabin," and
•" Time signal," which are subsidiary signals, which
have their origin in motives of economy or con-
venience.
Turning next to the dial signals, we find that the
majority, whilst indicating the fact that the permis-
sion accorded by the acceptance of the preliminary
•" Be ready " signal has been acted upon, are also
used to confirm the intimation conveyed by the
particular form of "Be ready" employed of the class
of traffic that is being forwarded ; and in all cases
we find that the information imparted is given in
greater detail than by the more general " Be ready "
signal. Of the sixteen signals provided for trans-
mission on the dials, twelve are used to indicate the
•character of the traffic being forwarded : one notifies
the clearance of the line for all classes of trains,
one is a " caution " signal, and the other two relate
to temporary fouling of the lines at a block station
<or cabin owing to shunting operations, which involve
crossing from one line to the other.
It is not proposed to analyse this code further,
.since, as already stated, it has been superseded ;
RAILWAY SIGNALLING. 47
but attention is called to the great proportion of
the signals which are considered necessary for the
description of traffic, and also of the order in which
the details are given. A further point that may be
referred to is that at least two of the bell signals
have no complement. Thus, the " Obstruction danger
signal " is not supplemented by any signal indicating
the removal of the obstruction. Similarly, there is
no signal provided where it is required to intimate
that a proffered " Be ready " cannot be accepted.
In this case the refusal to accept a " Be ready "
may appear to be of a negative character, and liable
to confusion with a failure of the bell circuit. As,
however, the " Call attention " signal precedes the
" Be ready," and must be acknowledged, the differ-
ence between this and a failure of apparatus is
evident. At the same time, there seems no valid
reason for the omission from the code of a signal
which indicates inability to accept the preliminary
signal.
REGULATIONS FOR TRAIN SIGNALLING BY BLOCK
TELEGRAPH SYSTEM ON DOUBLE LINES OF RAILWAY.
The object of the system of block telegraph signalling is to prevent more
than one train being on the section between two block signal cabins on
the same line at the same time.
The signalling of trains on the block telegraph system does not in any
way dispense with the use of fixed, hand, or fog signals, whenever and
wherever such signals may be requisite to protect obstructions on the line.
The signal cabins at which the block telegraph working is in operation
are furnished with instruments to signal for each line of rails, and the
system under which these instruments are to be worked, and the mode of
indicating the description of approaching trains, will be as given in the
following code of regulations.
All fixed signals must be kept at Danger, except when it is necessary
to lower them for a train to pass ; and, before any signal is lowered, care
RAILWAY SIGNALLING.
must be taken to ascertain that the line is clear, and that the block
telegraph and other regulations have been duly complied with.
When the block instruments are not in use, the handles must be kept
vertical ; the indicators will then hang vertically, and when in that position
will indicate Line blocked.
The block instruments must be used exclusively for the purposes shown
in the block telegraph regulations, and must not, except in case of accident,
be used for conversing. They must only be used by the signalman or other
person specially appointed for the duty.
The movements on the block instruments and bells must be made slowly
and distinctly, and the pauses between the sets of beats clearly marked.
BELL SIGNALS.
See Beats on
Regulations. Bell.
i Call attention I
f f Express passenger train, or break-
down van train going to clear the
line, or light engine going to assist
disabled train ? 4
Ordinary or excursion passenger
train, or breakdown van train not
going to clear the line ?
Branch passenger train ? (applicable
only where special instructions are
given)
Fish, meat, fruit, horse, cattle, or
perishable train, composed of
coaching stock, or for S.W.B. train? 5
Empty coaching stock train? 5
Fish, meat, or fruit train, composed
of goods stock, express cattle, or
express goods train ? 5
Ordinary goods, or mineral train
stopping at intermediate stations ? 3
Branch goods, mineral, or ballast
train? (applicable only where
special instructions are given) 3
Through goods— mineral or ballast
train ?
Light engine, or two light engines
coupled, or engine and not more
than two brakes ? 5
Ballast train, or other train requiring
3 -2
and \ §
4
3» 4:
8,
and
9
How to be given.
4 consecutively.
4 3, pause,
4 i, pause, 3.
5 consecutively.
2, pause, 2, pause. i~
5 i, pause, 4.
3 3 consecutively
3 I, pause, 2.
5, 4, pause, i.
2, pause, 3.
to stop in section, or platelayers'
lorry requiring to pass through
tunnel ? ..
5 i, pause, 2, pause, 2.
RAILWAY SIGNALLING.
49
3 (a) Train entering section 2 2 consecutively.
6 (a) Assistant engine in rear of train 4 2, pause, 2.
112 and 13 Obstruction removed 3 2, pause, I.
12 Obstruction danger 6 6 consecutively.
^ Inside home signal —
13 Blocking back .. , 6{ *> . Pauf' 4' .
j Outside home signal,
I, 3, pause, 3.
17 Stop and examine tram 7 7 consecutively.
18 Cancelling signal 8 3, pause, 5.
f 9 consecutively to
19 Train passed without tail lamp ... , 9{ cabin in advancf;.
y I 4, pause, 5, to cabin
V in rear.
20 Train divided ... 10 5, pause, 5.
21 Shunt train for following train to
pass ii i, pause, 5, pause, 5.
22 Vehicles running away on wrong
line 12 2, pause, 5, pause, 5.
5 (a) Section clear but station or
junction blocked 13 3, pause, 5, pause, 5.
23 Vehicles running away on right line 14 4, pause, 5, pause, 5.
24 Opening of signal cabin 15 5, pause, 5, pause, 5.
27 Testing block indicators and bells... 16 1 6 consecutively.
24 Closing of signal cabin 17 7, pause, 5, pause, 5.
28 (a) Time signal 18 8, pause, 5, pause, 5.
29 Lampman or fog-signalman required 19 9, pause, 5, pause, 5.
30 Testing controlled or slotted signals 20 5, pause, 5, pause,
5, pause, 5.
.'See Regulations. DIAL SIGNALS.
2 Signal correctly repeated I beat to right.
Signal incorrectly repeated I beat to left.
10 Train out of section 2 beats to right.
Express passenger train ; breakdown van \
train going to clear the line; fish,
meat, fruit, horse, cattle, or perishable I , ^ , ,
train composed of coaching stock ; f 2 beats to left'
engine and not more than two brakes, I
or S.W.B. train entering section J
C Ordinary or excursion passenger train ; \
breakdown van train not going to j
? onrl A clear line ; empty coaching stock ! ,
3 and 4 train ; fish, meat, or fruit train com- [3 ^is to left«
posed of goods stock ; express cattle, J
*• or express goods train entering section '
4
5O RAILWAY SIGNALLING.
Through goods, mineral, or ballast train \ , . f
entering section /4 b<
(Ordinary goods, mineral, or ballast j
train stopping at intermediate stations, t i i rf
"and 9. "I or platelayers' lorry going through | 5 D<
I tunnel entering section J
3 and 4 Light engine I beat to right and
3 to left.
3, 4, and / Two engines or trains coupled entering \ 3 beats to right and
7 \ section / 3 to left.
17 Caution 4 beats to right.
{Blocking back for passenger trains 2, pause, 2, pause,
2 to left.
Blocking back except for passenger trains 6 beats to left
Line clear after blocking back 6 beats to right.
25and27 Testing 16 beats to right and
left alternately.
1. Call Attention. — The call attention signal must always be
given before any other signal, except those marked (a), and must be
acknowledged immediately on receipt.
2. Repetition and Acknowledgment of Signals. — Except where
special instructions are issued to the contrary, no signal must be con-
sidered as understood until it has been correctly repeated to the signal
cabin from which it was received, and, in the case of dial signals, the
acknowledgment given that such repetition is correct. When the is line
clear signals are not acknowledged, they must be given again at short
intervals.
3. Mode of Signalling by Block Telegraph. — A, B, and C repre-
sent three consecutive block signal cabins, and the process of signalling
a train is as follows :
Prior to the dispatch of a train conveying passengers from A,
the signalman there, provided he has received the train out of
section signal for the previous train, and the block indicator be
in its normal position, must call the attention of B, and, having
obtained it, must give the proper is line clear signal ; if the
line be clear at B, the signalman there must acknowledge the
signal and peg the block indicator to the line clear position.
The signalman at A may then, if the line be clear, take off his signals
for the train to leave A.
On the train leaving A the signalman there must send the train
entering section signal to B, and the signalman at B must
RAILWAY SIGNALLING. 51
acknowledge the signal and peg the block indicator to train on
line.
B must then, provided he has received the train out of section
signal for the previous train, and the block indicator be in its
normal position, call the attention of C, and, having obtained it,
must give the proper is line clear signal to C. On receiving
permission from C for the train to approach, B may take off his
signals for the train to proceed to C, and as soon as the train
has passed the advance signal at B, or, where there is no advance
signal, has passed the home signal at least 400 yards, and is
continuing its journey in the next section, or has been shunted clear
of the main line at B, the signalman there must call the attention
of A, and, having obtained it, give the train out of section
signal to A.
Where the sections are short, the is line clear signal must be sent
forward, where necessary, to avoid delay to the train, as soon as
it has been acknowledged and before the train entering section
signal has been received from the rear, when this can be done in
accordance with the regulations under which the is line clear
signal is to be forwarded.
The same mode of signalling must be observed in regard to trains not
conveying passengers, except that the is line clear signal may be
offered to the advance cabin before the train out of section
signal has been received for the preceding train, provided the
latter is also a train not conveying passengers.
In foggy weather, or during falling sntxo, every train must be dealt
-sith as prescribed for passenger trains.
4. lane Clear, or Giving Permission for a Train to Approach. —
Unless special instructions are given to the contrary, the line must not be
considered clear, nor must a train be allowed to approach from the signal
cabin in the rear, in accordance with Regulation 3, except as prescribed in
Regulation 5, until the preceding train has passed the advance signal, or,
where there is no advance, has passed the home signal at least 400 yards,
and is continuing its journey in the next section, or has been shunted clear
of the main line, nor until all the points over which the approaching train
has to pass have been placed in their proper position, and the line is clear
for at least 400 yards ahead of the home signal.
Where the home signal at the signal cabin in advance is less than
400 yards ahead, permission for a train to approach must not be given
to the signal cabin in the rear until permission for the train to proceed
4*
52 RAILWAY SIGNALLING.
has been received from the signal cabin in advance, except in the
case of a train not conveying passengers, which may be accepted under
Regulation 5, when the advance section is not occupied by a train
conveying passengers.
After permission has been given for a train to approach in accordance
with Regulation 3, no obstruction of the line on which such train requires
to run must be allowed until the train has been brought to a stand at the
home signal, or has passed into the section in advance, or the cancelling
signal has been received from the signal cabin in the rear.
If the line be not clear, or if from any other cause the signalman be not
in a position to give permission for the train to approach when the signal-
man in the rear forwards the is line clear signal, that signal must not be
acknowledged until the signalman to whom the signal has been sent is
prepared to receive the train, when he must give permission for it to
approach in accordance with the prescribed regulations.
At Junctions, except where otherwise provided, the approach of trains,
which can cross or foul each other, is regulated as shown below.
SICNALCABIN SICNALCABIN SIGNAL CAB IN
A. B. C.
SIGNAL
CABIN
When permission has been given by B for a train to approach from C,
no train must be allowed to leave D until that from C has been brought
to a stand at the home signal or has passed through the junction, and is
beyond the advance signal, or, where there is no advance signal, has passed
the home signal a distance of 400 yards, and is continuing its journey, or
where the next signal cabin ahead is within 400 yards, until the is line
clear signal has been accepted by the signalman at that cabin, except as
provided for in the second clause of this regulation ; nor in such a case
must a train be allowed to leave A for D unless the junction facing points
OF THB
UNIVERSITY
RAILWAY SIGNALLIKh^^i ^ 53
at B are set for C, and the line towards C is clear to the advance signal,
or, where there is no advance signal, is clear for a distance of 400 yards
beyond the junction points, or, where the next signal cabin ahead is within
400 yards, until the is line clear signal has been accepted by the signal-
man at that cabin, except as provided for in the second clause of this
regulation.
When permission has been given by B for a train to approach from D,
no train must be allowed to leave C until that from D has been brought
to a stand at the home signal or has passed through the junction, and is
beyond the advance signal, or, where there is no advance signal, has passed
the home signal a distance of 400 yards, and is continuing its journey, or,
where the next signal cabin ahead is within 400 yards, until the is line
clear signal has been accepted by the signalman at that cabin, except as
provided for in the second clause of this regulation.
When permission has been given by B for a train to approach from A
for D, no train must be allowed to leave C until that from A has been
brought to a stand at the home signal, or has passed clear of the junction,
or the junction facing points have been set for C, and the line towards C
is clear to the advance signal ; or, where there is no advance signal, is clear
for a distance of 400 yards beyond the junction points, or, where the next
signal cabin ahead is within 400 yards, until the is line clear signal has
been accepted by the signalman at that cabin, except as provided for in the
second clause of this regulation.
When a train has been sent to the advance or starting signal and the
rear of the train is well clear of the junction, permission for a following
train to approach may be given by the signalman to the signal cabin in the
rear if the points are set for the following train to pass on to another line,
and that line is clear, and the instructions given in the preceding paragraphs
can be complied with.
In dealing with trains, neither of which conveys passengers, in clear
weather, and under ordinary circumstances, when approaching a junction
on sections which converge to a fouling point, either by running into one
line or by crossing each other to different lines, the mode of signalling
given in Regulation 5 must be adopted, except that if the block indicator
be in its normal position when the IB line clear signal is offered for a
second train, the junction signalman must, after accepting that signal by
giving the section clear but station or junction blocked signal, and
after that signal has been acknowledged, peg the indicator to train on
line, and after the train entering section bell signal has been received
and acknowledged, unpeg the indicator, when the dial signal must be given
in the usual way.
54 RAILWAY SIGNALLING.
5. Section Clear, but Station or Junction Blocked. — (This signal
must only be used in the case of trains conveying passengers where it is
specially atithorised by instructions from the general manager or the
superintendent of the line, and so far as regards light engines and trains
not conveying passen^ets is only applicable in clear weather and under
ordinary circumstances. ) When the line is clear to the home signal, and
it is necessary for a train to be allowed to approach cautiously for the
purpose of connecting at a junction or junction station, or in consequence
of an obstruction existing within the home signal, or owing to shunting
operations within the home signal, or from any other cause, the is line
clear signal must not be acknowledged in accordance with Regulation 3,
but the section clear but station or junction blocked signal must
be given, and acknowledged if the circumstances admit of this being
done, when, if the indicator be in the vertical position, it must be
pegged to train on line. The signalman receiving this signal must (it
the train has not already passed the home signal towards the starting
or advanced starting signal) bring the train to a dead stand at the
home signal, and verbally instruct the driver that the section is clear to
the next home signal, but that the station or junction ahead is blocked.
A green flag by clay and a green light by night must at the same time
be exhibited to the driver, and the necessary fixed signals lowered to
give permission for the train to proceed. The train entering section
bell signal must then be given, and acknowledged, after which the
block indicator must be unpegged, and the proper dial signals given
and acknowledged, and the indicator again pegged to train on line.
The train out of section signal must not be given until both trains
have passed out of the section. Even for connecting piirposes two
passenger trains must not be allowed to approach a junction at the same
time on lines which converge to a folding point.
Where authority is given for passenger trains to be allowed to enter
the advance section under this regulation, the is line clear signal, for
the train which requires to be sent forward to make the connection,
may be offered before the train out of section signal has been
received for the train with which the connection has to be made.
Where the home signal is at such a distance from the signal cabin
that it is not possible for the signalman to communicate verbally with
the driver when the engine is standing at the home signal, the signal-
man must, after bringing the train to a dead stand at the home
signal, lower it to allow the driver to draw up to his signal cabin, and
must stop the train at the signal cabin by exhibiting a red flag by day
.and a red light by night. The driver must then be verbally instructed
RAILWAY SIGNALLING. 55
that the section is clear to the next home signal, but that the station
or junction ahead is blocked ; after which a green flag by day and a
green light by night must be exhibited to the driver, and the necessary
fixed signals lowered to give permission for the train to proceed.
If a train is assisted by an engine in the rear, a green flag by day
and a green light by night must also be exhibited to the driver of the
engine in the rear of the train.
Except where special instructions are issued to the contrary, when a
train has passed the signal cabin and is brought to a stand at the
starting signal or the advanced starting signal, the driver must under-
stand that the lowering of the starting signal or the advanced starting
signal is an indication that the line is only clear to the home signal at
the signal cabin in advance, and that he must regulate the speed of his
train in the same way as if he had been verbally instructed to proceed
under the section clear but station or junction blocked signal.
When some time is likely to elapse before the train for which the
is line clear signal has been sent will be ready to enter the section,
the section clear but station or junction blocked signal must not
be acknowledged, but when the train is ready to enter the section, and
before it is allowed to do so, the is line clear signal must be again
sent in order to give the signalman at the cabin in advance an oppor-
tunity of receiving the train under Regulation 3, if the circumstances
are so altered as to admit of his doing so ; if they are not, he must
again give the section clear but station or junction blocked signal,
which must be acknowledged, and the signalman at the rear cabin must
not allow the train to proceed until this has been done.
6. Assistant Engine in Rear of Train. — After the train entering
section signal has been given to the signal cabin in advance, and the
indicator has been pegged to the train on line position for a train that
is assisted by an engine in the rear, the assistant engine in rear of
train signal must be given to the signal cabin in advance, to indicate
that an engine is assisting the train in the rear. The assistant
engine in rear of train signal must be acknowledged by being repeated,
and a note of the signal must at once be made in the train register
book at the signal cabin in advance, and the train out of section
signal must not be given until the assisting engine has arrived. (This
regulation only applies at places ~nhere the use of assistant engines is
specially authorised.)
7. Engines or Trains Coupled. — Whenever it may be necessary to
detach one engine or train from another on the main line, the driver
of each engine requiring to be detached must, before uncoupling, verbally
56 RAILWAY SIGNALLING.
communicate with the signalman and make him clearly understand what
is about to be done, and in what direction the uncoupled engine or
train will proceed. Engines or trains must only be coupled or uncoupled
at signal cabins and then only during daylight.
8. Ballast Train requiring to Stop in Section. — When a ballast
train has to stop in a block section for permanent-way purposes, the
signalman must give the prescribed is line clear signal, and the signalman
at the cabin in advance must, if the line be clear to the home signal, give
permission for the train to approach his cabin in accordance with Regulation 5*.
When a ballast train, which has been signalled as a through ballast train,
requires to stop in the section for permanent-way purposes, and comes to a
stand at a signal cabin to enable the guard to inform the signalman that
his train is going to stop on the main line in the section in advance (see
Rule 320 in the Book of Rules and Regulations}, the signalman must give
the cancelling signal, and when the signal has been acknowledged, he
must signal the train as a ballast train requiring to stop in section.
This regulation also applies to goods or mineral trains stopping at sidings
between stations.
9. Platelayers' Lorries going through Tunnels. — When it is
necessary for a platelayers' lorry to go through any of the tunnels
specially enumerated in the appendix to the working time table as
coming within the application of this regulation, it must be signalled on
the block instruments in accordance with the authorised code, and the
signalman at the cabin in advance must, if the line be clear to the home
signal, give permission for the lorry to approach his cabin in accordance
with Regulation 5. No train must be allowed to enter the tunnel on the
same line until the train out of section signal has been received from
the signal cabin in advance to indicate that the lorry has left the tunnel
and has passed the next block signal cabin, or been taken off the rails.
Should the lorry, after passing through the tunnel, be removed from the.
rails before reaching the next signal cabin, the ganger must go forward and
inform the signalman that the lorry is clear of the line.
If, however, time would be saved, the ganger must return to the signal
cabin in the rear and inform the signalman that the lorry is clear of the
line ; the signalman must then send the cancelling signal to the signal
cabin in advance.
10. Train Out of Section. — Trains must not be considered out of
section and the train out of section signal must not be given to the
signal cabin in the rear until the last vehicle of the train (or the last vehicle
of the slip portion of the train |or the assistant engine) with tail lampv
attached, has passed the advance signal, or, where there is no advance.
RAILWAY SIGNALLING. 57
signal, has passed the home signal 400 yards, and is continuing its journey
in the next section, or has been shunted clear of the main line.
When the last vehicle of a train does not pass the signal cabin before it
has been shunted into a siding, the signalman must, before giving the train
out of section signal, ascertain from the guard or shunter in charge of the
train that the whole of the train, with tail lamp attached, has arrived, and
the guard or shunter will be held responsible for giving this information to
the signalman ; the fireman being similarly responsible in the case of a light
engine.
11. Course to be pursued when a Train is an unusually Long
Time in a Section. — Should an unusual time elapse after the train
entering section signal has been received without the train so signalled
coming in sight, the signalman must, if there is a tunnel in the section in
which the train is running, prevent any train in the opposite direction
proceeding on its journey until he has ascertained that the line on which it
has to run is clear ; and if there is no tunnel in the section, the signalman
must stop the first train proceeding in the opposite direction, and inform
the driver of the circumstance, and, after the necessary signals have beerv
sent and acknowledged, instruct him to proceed with caution.
12. Obstruction Danger Signal. — Should it be necessary, in conse-
quence of obstruction or other cause, for an approaching train to be stopped
at the signal cabin in the rear, the obstruction danger signal must be
given to that cabin, and the signalman there must immediately exhibit the
danger signal and take the necessary measures to stop the approaching
train ; he must not allow the train to proceed until he has received from
the signal cabin in advance the obstruction removed signal, nor until
the proper block signals have been sent and acknowledged.
The signalman forwarding the obstruction danger signal must place
the block indicator for the line or lines affected to train on line if not
already in that position, and must also place or maintain his signals at.
danger to protect the obstruction.
Should there be reason to suppose that both lines are fouled, the signal-
man must send the obstruction danger signal in both directions, and.
where there are parallel running lines the requisite steps must be taken to
stop the trains running on any line that may possibly be obstructed.
Should a signalman receiving the obstruction danger signal succeed
in stopping a train for which the is line clear signal has been accepted
by the signalman at the cabin in advance, he must at once advise the
signalman at that cabin by giving the cancelling signal. This signal
must be acknowledged, but the block indicator must be maintained at the
train on line position until the obstruction has been removed.
58 RAILWAY SIGNALLING.
13. Blocking Back. — When it is necessary, after the passing of one
train and before giving permission for another to leave the signal cabin
in the rear, to obstruct the line inside the home signal, by crossing a
train or vehicles from one line to another for shunting purposes, or by
allowing vehicles, or a train which is not about to proceed on its journey
at once, to leave an independent line, or a siding, for the main line,
the blocking back signal (2 — 4) must be given to the signal cabin or
cabins in the rear, and, on this being acknowledged, and the dial signal
given and acknowledged, the block indicator for the line or lines intended
to be occupied must be pegged to the train on line position.
The same course must be pursued before the line is obstructed outside
the home signal.
When a signalman asks permission to occupy the line outside his
home signal, he must give the blocking back signal (3 — 3) to the
signalman at the cabin in the rear, and the latter must, before acknow-
ledging the blocking back signal (3—3), satisfy himself that he can
with safety give such permission, and that he has not allowed a train
to approach his signal cabin from the signal cabin in the rear under
Regulation 3, unless there be a distance of at least half a mile between
his home signal applicable to such train and the signal cabin from which
he has received the blocking back signal, or, if at a junction, unless
he has set his facing points for another line, and that line is clear
according to these regulations.
If a signalman has allowed a train to approach his cabin from the
signal cabin in the rear under Regulation 3, and there is not at least a
distance of half a mile between his home signal and the home signal at
the cabin from which he has received the blocking back signal (3 — 3),
he must not acknowledge the latter until the approaching train has been
brought to a stand at his home signal. Should he not have accepted
a train, he must not acknowledge the blocking back outside home
signal signal (3—3) until he has offered the blocking back inside
home signal signal (2 — 4) to the cabin in the rear and it has been
acknowledged.
When a signalman offers the blocking back signal, and the signal-
man at the cabin in the rear is not in a position to give permission for
the line to be occupied, he must not repeat the blocking back signal,
-or acknowledge it in any way, and until the signal has been acknow-
ledged, the line must not be occupied.
When a passenger train, or vehicles containing passengers, is about to
be shunted from one main line to another, or a passenger train which
is not about to proceed on its journey at once is allowed to pass from
RAILWAY SIGNALLING. 59
an independent line or a siding to the main line, the signalman must
give the blocking back l>ell signal to the rear cabin and the following
distinctive dial signal : six beats of the indicator to the left, divided
into 2 pause, 2 pause, 2, so that the rear signalman may know with
what kind of train the line in advance is occupied. The block indicator
for the line or lines intended to be occupied must then be pegged to
the train on line position.
Trains or engines approaching a junction on a line converging to a
fouling point, or when leaving an independent line, or a siding, to at
once proceed on their journey, or crossing directly over another running
line, are exempted from the operation of blocking back, and must be
dealt with under Regulation 4.
Unless special permission be given by the general manager or the
superintendent of the line, no train or vehicle mtist be placed oittside
a home signal where the line is on a falling gradient towards the signal
cabin in the rear.
When the obstruction has been removed and the main line or lines
are again clear, the obstruction removed bell signal must be given to
the signal cabin in the rear, and on acknowledgment the dial signal
line clear after blocking back must be given and acknowledged.
Should a train have been accepted under Regulation 5, and in addition
to the obstruction having been removed the train has passed out of the
section, the obstruction removed bell signal and the train out of
section dial signal must be given.
When shunting operations have ceased outside the home signal, and
are required to be continued inside that signal, the obstruction removed
bell signal (2—1) and the dial signal line clear after blocking back
must be given and acknowledged. The signal for blocking back
inside the home signal must then be offered and accepted.
The signalmen forwarding and receiving the blocking back signal
must make a note of the circumstance in their train register book.
14. Section Obstructed by Accident or by Disabled Train.
Should a signalman receive information from the fireman or guard of a
disabled train that a second train is required to enter the section to
assist the disabled train, or should it be necessary for the breakdown
van train to enter a section obstructed by accident or otherwise, the
second train or breakdown van train, as the case may be, may, after
having been brought to a stand and the driver informed of the circum-
stances, be allowed to enter the section under the following arrangements :
The signalman must inform the signalman at the cabin in advance of
the circumstances, and give the train entering section signal on the
6O RAILWAY SIGNALLING.
bell to the signal cabin in advance, and, after it has been acknowledged
he must note the circumstances in his train register book, and ther*
allow the second train to enter the section. The signalman at the cabia
in advance must also note the circumstance in his train register book,
and must not give the train out of section signal until both trains
have passed out of the section in accordance with Regulation 10. The
guard of the train requiring assistance must ride on the engine of the
second train, and point out to the driver the position of the disabled
train. The second train must run at reduced speed, and great caution
must be observed by all concerned. When the train out of section
signal is received from the signal cabin in advance, and permission has
been obtained for another train to proceed, such other train must be
stopped at the signal cabin in the rear, and the driver instructed to
proceed cautiously through the section.
15. Breakdown Van Trains and Engine Replacing or Assisting
Disabled Engine. — To prevent delays, breakdown van trains when
proceeding to clear the line must be signalled as express passenger
trains, the shunt train for following train to pass signal being
given whenever the sections in advance are occupied by trains which the
breakdown gang must pass to reach the scene of accident.
The same course must be adopted in the case of one engine proceeding
to take the place of another that has failed, or of an engine, with or
without a train, when sent forward to render assistance in case of failure
or accident to preceding trains.
16. When Block Telegraph may be Suspended for Single-Line
Working. — Should any obstruction occur necessitating the working of
single line, and it is necessary to suspend block telegraph working, this
must be done only by an order in writing from the person in charge who
arranges the single-line working ; but during foggy weather or falling snow,
or when a tunnel intervenes, or the gradients are heavy on the section ot
the line where the traffic has to be worked on a single line, block telegraph
working must be maintained, the up trains being signalled on the up-line
block telegraph circuit, and the down trains on the down- line block tele-
graph circuit, or the pilotman must accompany every train passing over the
single line. On the working of the double line being resumed, any order
suspending the working of the line by block telegraph is to be cancelled by
a written notice in the same manner and at the same time as the order for
working single line is cancelled. The same process must be observed as in
the case of resumption of block working after failure of instruments or bells-
17. Stop and Examine Train. — If a signalman observes anything
unusual in a train during its passage, such as signals of alarm by a passenger,.
RAILWAY SIGNALLING. 6 1
goods falling off, a vehicle on fire, a hot axle-box, or other mishap, except a
tail lamp missing or out, or a train divided, for arrangement as to which
see Regulations 19 and 20, or if a light engine should pass out of a section
when the signal for a train has been received, he must give to the signalman
at the signal cabin in advance the stop and examine train signal, and
must himself exhibit his signals to stop any train coming in the opposite
direction ; and the signalman at the signal cabin in advance must acknow-
ledge such signal, and immediately exhibit the danger signals to stop any
train coming from or going towards the signal cabin from which the signal
was received. The train, when stopped, must be carefully examined and
dealt with as occasion may require ; should any train going in the opposite
direction have been stopped, it must be allowed to proceed after satisfactory
evidence has been obtained that the line on which it is about to run is not
obstructed.
The signalman sending the stop and examine train signal must not
give the train out of section signal to the cabin in the rear, but, after
calling attention, give the cantion signal, and again peg the indicator to
train on line. Before the next train or engine is allowed to enter the
section, the signalman at the rear cabin must offer the is line clear signal,
and if the signalman at the cabin in advance is in a position to accept the
train or engine he must again give the cantion signal, which must be
acknowledged by the signalman at the cabin in the rear, who must stop
the train or engine and warn the driver to proceed cautiously, informing
him why it is necessary that he should do so. He must then give the bell
signal train entering section, which must be acknowledged, where-
upon the signalman at the advance cabin will release the indicator, and the
dial signal according to the description of train entering the section must
be given by the signalman at the rear. When the train or engine which was
cautioned into the section has passed out of the section at the advance
cabin, the signalman there will recommence signalling in the ordinary way.
Should either signalman have reason to believe in the case of a vehicle
being off the rails, or goods falling from the train, that the permanent
way has been damaged or fouled, he must not allow any train to pro-
ceed in the direction of the obstruction until the line has been examined
and he is satisfied that it is safe for the passage of the train.
Should the signalman who receives the stop and examine train
signal be unable to ascertain after examination of the train why the signal
was sent, he must inform the driver of the first train travelling in the
opposite direction of the circumstances, and instruct him to proceed
cautiously to the next signal cabin.
Where practicable, the signalman must also telegraph or telephone the
62 RAILWAY SIGNALLING.
signal cabin in advance the cause of sending the stop and examine
train signal. Signalmen must be careful to notice each train as it
passes, to ascertain whether there is any apparent necessity for having it
stopped at the next signal cabin for examination.
1 8. Cancelling Signal. — Should it be necessary to cancel the is line
clear or train entering section signal, the cancelling signal must be
forwarded, and the signalman receiving the signal must, after acknow-
ledging it, place the block indicator in the vertical position, unless the
cancelling signal has been forwarded to cancel a signal accepted under
Regulation 5, in which case the indicator must be kept at train on line
until the section is clear, and an entry must be made in the train
register book showing what signal was cancelled, and at what time.
The cancelling signal must not be used unless the is line clear or
train entering section signal has been accepted or acknowledged.
19. Train Passed without Tail Lamp. — All trains and light engines
will carry a tail lamp in the rear, both by clay and by night, to indicate
to the signalmen that no vehicle has become detached on the journey,
and signalmen must carefully watch each train as it passes, and satisfy
themselves that it is complete before giving the train out of section
signal to the signal cabin in the rear. Should a train pass a signal cabin
and the signalman be unable to satisfy himself whether or not the tail
lamp is on the train, he must immediately exhibit the danger signal,
and stop the first train going in the opposite direction, informing the
driver what has occurred, and instructing him to proceed cautiously so
as to avoid danger in the event of any portion of the train having fouled
the line on which he is running. The signalman must also send the
train passed without tail lamp signal (nine consecutive beats) to the;
signal cabin in advance, and must not give the train out of section
signal to the signal cabin from which the train without tail lamp has
arrived, but must call the attention of the signalman there in the usual
manner, and, on gaining his attention, must give the train passed
without tail lamp signal (4—5).
In such a case the signalman at the cabin in the rear may offer the
is line clear signal for a following train although he has not received
the train out of section signal.
The signalman at the cabin in advance, on receiving the train passed
without tail lamp signal, must acknowledge it, and place the signals
at danger to stop the approaching train, advising the guard and driver
of the circumstances. If, where the sections are short, a signalman
receiving the train passed without tail lamp signal of nine consecu-
tive beats, finds that he cannot stop the train except by bringing it to
RAILWAY SIGNALLING. 63
a sudden stand, he must not place his signals to danger, but, as the
train is approaching, send the train entering section signal to the
signal cabin in advance and immediately follow it with the train passed
without tail lamp signal.
When the signalman who sent the train passed without tail lamp
signal (4 — 5) receives the is line clear signal for the next train or
engine requiring to enter the section (unless in the meantime he has
received intimation from the signal cabin in advance that the train has
arrived complete), he must not acknowledge it in the usual way, but if
he be in a position to accept the train or engine, he must repeat train
passed without tail lamp signal (4 — 5), the indicator remaining
pegged at train on line. The signalman in the rear receiving this
signal must stop the train and verbally instruct the driver to proceed
cautiously to the next signal cabin in advance, informing him why it is
necessary that he should do so, and then give the bell signal train
entering section. The signalman in advance must then unpeg the
indicator, upon which the proper dial signals will be given from the
rear cabin, and after they have been acknowledged, the indicator must
be again pegged to train on line. As soon as the train, the driver of
which has been cautioned, has passed the signal cabin from which the
train passed without tail lamp signal was sent, the signalman there
must give the train out of section signal, and the signalling of the
trains must then be resumed in the ordinary manner.
Should, however, the signalman sending the train passed without
tail lamp signal receive an intimation from the signal cabin in advance
that the train has arrived complete, he must, if he has not in the mean-
time given permission for a following train to leave the signal cabin in
the rear, call the attention of the signalman at that cabin and give the
train out of section signal.
If a train should pass with a tail light out when it should be burning,
and the signalman can plainly see the lamp, and is satisfied that the
train is complete, he must give the train out of section signal to the
signal cabin in the rear, and the train passed without tail lamp
signal (nine consecutive beats} to the signal cabin in advance, and, where
practicable, also telegraph or telephone to the signal cabin in advance,
stating that the lamp is not missing, but out. In such a case it will
not be necessary for the signalman sending the signal to stop any train
going in the opposite direction, but the signalman in advance must stop
the approaching train and inform the guard of the circumstances.
Should a train that is appointed to convey a slip portion pass a signal
cabin short of the proper slip tail signals (unless it be the cabin imme-
'64 RAILWAY SIGNALLING.
diately preceding the station where the portion has to be slipped, for
instructions as to which see following clause), the signalman must assume
that the slip portion has become detached, and send to the signal cabin
ahead the train divided signal, and to the signal cabin in the rear the
train passed -without tail lamp signal ; if the signalman in advance
finds on the arrival of the train that the slip portion has broken away,
he must telegraph or telephone to the signal cabin ahead, slip portion
broken away, train travelling without it ; and this message must be
repeated from signal cabin to signal cabin, as the train passes, as far as
the slip portion would have run, the train itself being signalled and
the line cleared in the usual way. Should the slip portion be afterwards
:sent on by special engine it must be signalled as a passenger train.
Should a train that is appointed to convey a slip portion be short of
the proper slip tail signals when it passes the signal cabin next in rear
of the station at which the portion is to be slipped, the signalman must
not send forward the train divided signal, but must only send the
train passed without tail lamp signal to the signal cabin in the rear.
He must then ask the signalman in advance on the speaking instrument,
has slip portion arrived complete? If the reply is "Yes," he must
send the train out of section signal to the signal cabin in the rear ;
but if the answer is "No," he must immediately telegraph or telephone
to the signal cabin in the rear, slip portion not arrived.
20. Train Divided. — This signal must be sent to the signal cabin in
advance in the event of a signalman observing that a train has become
divided, and is running in two or more parts. If the train is assisted
by an assistant engine in the rear, or is running on a falling gradient
• or between short sections, where the stoppage of the first part would
risk a collision with the second part, the signalman receiving such signal
must immediately exhibit the danger signal to stop any train going
towards the signal cabin from which the signal was received, but if the
line on which the divided train is running is clear ahead for it to run
upon, he must not exhibit the signals to stop the first portion, but must
:give the driver a green signal either by flag or hand lamp as occasion
may require, waving the signal slowly from side to side. The driver, on
. seeing the green signal waved slowly from side to side, will understand
that his train is divided and must exercise great caution by looking out
for the second portion, and unless he has reason to believe the line is
not clear ahead, must not stop the portion attached to his engine until
he is satisfied that the rear portion has been stopped, or is running very
slowly. He must, however, observe and obey any signals that may be
• exhibited against him. So soon as the first portion of the train has
RAILWAY SIGNALLING. 65
passed, the signalmen sending and receiving the train divided signal
must take proper measures for dealing with the second portion, and
place detonators on the rails to attract the attention of the guard, or of
the assistant engine-driver should there be an assistant engine in the rear.
If the divided train is running on a rising gradient, or where the line
is level, and is not assisted by an assistant engine in the rear, the
signalman receiving the signal must exhibit the danger signal to stop
any train coming from or going towards the signal cabin from which the
signal was received. The first portion of the divided train, when stopped,
must be shunted into a siding as expeditiously as circumstances will
permit, or otherwise dealt with as may be necessary to prevent the
second portion coming into collision with it.
Should any train going in the opposite direction have been stopped,
it must not be allowed to proceed until it has been ascertained that the
line on which it is about to run is not obstructed. Should a train
become divided in starting, and the driver run forward with the first
portion, leaving the rear portion stationary, the stop and examine
train signal must be sent to the signal cabin in advance, and not the
train divided signal.
21. Shunt Train for Following Train to Pass. — This signal must
be used to prevent important trains being delayed by less important trains.
When, before the train out of section signal has been received from
the signal cabin in advance for the last train, the signalman receives a
signal from the cabin in the rear for a more important train, the shunt
signal must be sent to the signal cabin in advance, and the signalman
there, on receiving this signal, must take the necessary measures to
clear the line so as to prevent delay to the second train. He must use
his discretion as to the best means of effecting the object in view, and if
he is unable, from any cause, to shunt the train at his signal cabin, or
if he thinks it inexpedient to do so, he must allow the train to proceed,
and send forward the shunt signal to the signal cabin in advance. The
signalmen forwarding and receiving the shunt signal must make a note
of it in their train register books.
22. Vehicles Running Away on Wrong Line.— Should any vehicle
or portion of a train be running back in the wrong direction, or should
a train be proceeding on the wrong line, the signalman must immediately
exhibit the danger signal and call the attention of the signalman at the
next cabin towards which the vehicle, train, or portion of the train, may
be running, by giving the vehicles running away on wrong line
signal ; he must also stop the first train going in the same direction on
the right line, and, after informing the driver what has occurred, instruct
5
66 RAILWAY SIGNALLING.
him to proceed cautiously. The signalman in the rear receiving this-
signal must immediately exhibit the danger signal to stop any train
coming from or going towards the signal cabin from which the signal
was received, and take any other measures that may be necessary, such
as turning the runaway train or vehicles across to the other line, or into
a siding, as may be most expedient under the circumstances. In the
event of a runaway train or vehicles being turned across to the other line,
the vehicles running away on right line signal must be passed on to
the next signal cabin. Should the signalman be unable to take such
protective measures, he must pass on the vehicles running away on
wrong line signal to the next cabin in the rear ; he must also place
detonators on the rails to attract the attention of the men in charge of
the train or portion of the train.
Should any train travelling in the opposite direction be stopped, it
must not be allowed to proceed until it has been ascertained that the
line on which it is about to run is not obstructed.
The signalman at the cabin from which the runaway train has started,
or any other signalman whose cabin may be passed by the runaway
train, must immediately give the obstruction danger signal to the
signalman in the rear before giving the vehicles running away on
wrong line signal, as prompt action on the part of both signalmen may
prevent a mishap. Should the signalman receiving the obstruction
danger signal succeed in stopping the train or engine for which he has
given the is line clear signal, he must at once advise the signalman in
advance by giving the cancelling signal.
23. Vehicles Running Away on Right Line. — If any train, vehicle,
or portion of a train has escaped and is running away in the proper
direction on the right line, or has entered the section without authority,
the signalman at the cabin in advance must be advised of the fact by
the signalman at the cabin in the rear giving the vehicles running
away on right line signal. The signalman forwarding this signal
must immediately exhibit the danger signal to stop any train coming
from or going towards the signal cabin towards which the vehicle or
train is running, and the signalman receiving the signal must also
immediately exhibit the danger signal to stop any train coming from or
going towards the signal cabin from which the signal was received (unless
there is a train in block in the same section as the runaway vehicle or
train and in front thereof, in which case, if the line be clear, such train
may be allowed to pass the signals before they are exhibited to stop the
runaway train), and he must arrange for the line on which the vehicle
or train is running to be cleared, and, if necessary, send the signal.
RAILWAY SIGNALLING. 67
forward, and to take such other measures as he may consider most
expedient under the circumstances. Should any train travelling in the •
opposite direction be stopped, it must not be allowed to proceed until
satisfactory evidence has been obtained that the line on which it is about
to run is not obstructed.
24. Opening and Closing of Cabins. — At a signal station or cabin
which is closed during the night, the signalman, on commencing duty in
the morning, and when going off duty at night, must give the appointed
signals in each direction, and an entry of the time these signals are sent
and acknowledged must be made in the train register books at each
cabin. Any defect in working must be noted in the occurrence book,
and at once reported by the signalman to the stationmaster, who must
immediately acquaint the telegraph linemen of the circumstance.
Opening and Closing of Signal Cabins and Stations where
there are Telegraphic Switches. — The signalman, before switching
the telegraphic apparatus out of circuit, must see that all the block
indicators are in a vertical position ; he may then give the closing signal
in both directions, and upon acknowledgment turn the switch handle
down to the right-hand side. Immediately after a cabin has been closed,
the testing signals must be given by the signalmen at the cabins placed
in circuit.
No engine, train, or vehicle must under any circumstances be allowed
to pass from one main line to another, or to enter upon the main lines
at a cabin which is switched out of circuit.
On resuming duty the signalman must examine the block instruments
to ascertain if any trains are signalled on the through section ; this will
be shown by the block indicators which are not turned out of circuit.
If a train is in the section he must, before switching the telegraphic
apparatus into circuit, peg the block indicator corresponding with the
line on which the train is travelling in the proper position, and then
turn the switch handle to the vertical position and give the opening
signal in both directions. The signals received for the train in question
must be transmitted to the next cabin then open in the direction the
train is proceeding.
25. Failure of Instruments or Bells. — In the event of any failure
of the instruments or bells, so that the necessary signals cannot be for-
warded and received, no train must be allowed to pass a signal cabin
into that section of the line where the failure exists, without having
been previously brought to a stand, and the driver and guard or guards
advised of the circumstance, and how many minutes the preceding train
is in advance. The driver must then be instructed to proceed cautiously,
5*
68 RAILWAY SIGNALLING.
in order to stop short of any obstruction there may be on the line.
Where there are no speaking instruments or when the speaking instru-
ments have failed, the driver of the first train thus warned must be
instructed to stop at the signal cabin in advance, and inform the signal-
man there that the bells or instruments have failed at the signal cabin
in the rear.
No train must be allowed to follow another train within five minutes,
unless the signalman sees that the section ahead is clear, and when a
tunnel intervenes in a block section, not within ten minutes, unless the
signalman can satisfy himself that the tunnel is clear ; in both cases the
driver must be stopped and cautioned as above directed. Steps must
be immediately taken to have the telegraphic apparatus put into working
order, and when the failure has been remedied, and the instruments are
again in working order, the testing signals must be given and acknow-
ledged, after which the indicator must be pegged to train on line.
The driver of the next engine allowed to proceed through the section
cautiously must be supplied with a written notice to the effect that it is
the last engine cautioned ; the number of the engine must also be given,
and the driver instructed to stop at the next signal cabin then open,
and hand the notice to the signalman. The signalman receiving this
notice must give the train out of section signal to the signal cabin
in the rear, and the signalling must then be recommenced in accordance
with these regulations.
26. Recording Time when Signals are Forwarded and
Received. — Except where special instructions to the contrary are issued,
the time at which all signals are forwarded and received must be made
legibly, with a pen, in the train register book, and the signalman on
duty must place his name immediately under the last entry made by
him at the expiration of his hours of duty.
If an incorrect entry be made, a line must be drawn lightly through
it, and the correction made above or below it, so that the original entry
may be clearly seen.
In recording the time at which signals are received and forwarded,
fractional parts of a minute less than half a minute must not be counted,
and the half minute and fractional parts more than half a minute must
be reckoned as a minute, thus : 15^ minutes must be entered as
15 minutes only, and 15^ minutes as 16 minutes.
27. Testing Block Bells and Indicators. — This signal must be
used to ascertain whether the bells and indicators are in perfect order,
and only when no train has been signalled. The bell testing signal
must precede the block indicator testing signal.
RAILWAY SIGNALLING. 69
28. Time Signal. — Signalmen receiving this signal on the speaking
instruments at 10 a.m. must communicate the information to the signal
cabins which do not receive it on the speaking instruments, by giving
the time signal on the bell. Signalmen must regulate their clocks
accordingly.
29. Lampman or Fog-Signalman Required. — At cabins where a
lampman or fog-signalman cannot be communicated with by the signal-
man on duty, the signal lampman or fog-signalman required must
be given to the cabin where the man required can be communicated
with. The signalman receiving such signal must at once inform the
stationmaster or person in charge in order that the necessary assistance
may be given.
30. Testing Controlled or Slotted Signals. — Signals which are
slotted from another block signal cabin must be tested as soon after the
signalmen change duty as the running of the trains, or, where there are
level crossings, the road traffic will permit. The signalman in charge of
the controlled or slotted signal, after releasing the lever so far as he is
concerned, must give 20 strokes on the bell (thus : 5 — 5 — 5 — 5) to the
signalman at the block signal cabin from which the signal is slotted. This
must be repeated, and the signal lever worked three times slowly. Each
signalman must make an entry in his train register book of the trans-
action, and if the wire working the slot requires adjusting, the signalman
going off duty must walk to the other block signal cabin and see it put
right, unless he can get this done by sending a message on the speaking
instrument or otherwise. Controlled or slotted signals must not be tested
after the is line clear signal has been received for a train on the line
to which they refer.
31. Parallel Lines. — With reference to Regulations 12, 17, 19, 20,
22, and 23, where there are parallel running lines, the necessary steps
must be taken to stop or caution the trains running on any lines that
may possibly be obstructed by what has occurred.
32. Mixed Trains conveying passengers and goods must be signalled
and dealt with as passenger trains.
33. Public Level Crossings. — Traction or other heavy engines, or
heavy loads of timber, etc., must not be allowed to pass over level
crossings at block signal cabins after permission has been given for a
train to approach from the signal cabin in the rear, nor until the line has
first been blocked back in all directions in accordance with Regulation 13.
The is line clear signal must not be accepted after permission has been
given for a traction or other heavy engine, or a heavy load of timber, etc.,
to cross until the obstruction is clear of the line.
7O RAILWAY SIGNALLING.
34. Travelling Cranes. — The lines must not be allowed to be fouled
by the jibs of travelling cranes, nor by the loading or unloading of
round timber, long timber, angle iron, or other articles of great length,
until the blocking back signal has been given and acknowledged in all
directions.
The sample code and regulations given on pages
46 to 69 was issued early in 1896, and superseded
the code which has just been considered, and forms
on close acquaintance a striking contrast with its
predecessor. The thirty-five signals which form the
total of the 1891 code for all purposes are in this
code replaced by a total of forty-five, or an increase
of over twenty - seven per cent, on the former
number. The number of regulations respecting the
use of the code is increased from eighteen to thirty-
four for all purposes, an increase of nearly eighty-nine
per cent, on the former number. The salient points
of difference in the two codes will be found in the
number, character, and order of the descriptive signals
employed. The four " Be ready " signals of the 1891
code are replaced by eleven " Is line clear " signals in
that of 1896, whilst the twelve descriptive dial signals
of the former are replaced by six similar signals in
the latter. Practically the change amounts to a
complete inversion of the order of importance of the
descriptive signals. In the 1891 code a descriptive
signal, indicative of a certain general class of train,
was sent first on the bell, and more detailed informa-
tion was afforded by the more distinctive dial signal.
In the 1896 code we find this order completely
reversed : the detailed signals are given by the pre-
liminary "Is line clear" signal, and the corresponding
dial signal is merely confirmatory in a general way.
RAILWAY SIGNALLING. 71
The change of title of the preliminary bell signal
from " Be ready " to " Is line clear," and of " On
line " to " Train entering section," is an instance of
the recognition of the necessity for precise language
in drawing such codes ; and the ample description of
the object and limits of such signalling, the precise
and decided instructions for their use, show to what
an extent the requirements have been studied.
Another point of difference is the character of the
signalling by which the bell signals are increased from
nineteen in the old code to thirty-three in the new,
without making the latter cumbrous by the use of an
inordinate number of blows of the hammer of the
bell. In the old code the greatest number of blows
constituting one signal was eighteen ; in the new code
the maximum number of blows is twenty, although the
number of distinctive signals to be sent is seventy per
cent, greater than with the older code. There is of
course nothing new in giving distinctness to a signal
.by breaking it up into sections, as is here done, and
as had been previously done in other places; but
its effect in producing the very necessary distinctness
might be made marked. Take, for instance, the two
signals relating to vehicles running away in both
codes. These two signals are so obviously the counter-
part of each other, that they should naturally follow
each other in the code. We find, however, sand-
wiched between them a signal relating, not to an
emergency, as these two do, but to what is a
•common* incident of working ; and the arrangement
is obviously necessary in order to obtain the neces-
sary distinction to ensure the difference being noticed.
72 RAILWAY SIGNALLING.
At the same time it must be admitted that in the
instance given full advantage has not been taken of
the distinctness that may be obtained from this
method of breaking up a signal into regular or
irregular sections, since the difference between the two
is precisely the same as in the older code.
Many of the signals which appear in the 1891
code are of course reproduced in that of 1896. Of the
fourteen additional bell signals, seven are additional
preliminary signals, one is a transference from the
dial signals of the old code (" Assistant engine in rear
of train"), two are additions to the emergency signals,
two are connected with temporary fouling of the
line by shunting operations, and two are of the class
which is not directly connected with the working of
traffic.
Of the dial signals, the title of " On line " has
been altered to " Train entering section," which
more nearly expresses the actual condition of things,
and we find that the number of such signals has
been reduced from twelve to seven. Two new signals
involving a change of procedure (" Signal correctly
repeated," "Signal incorrectly repeated") are intro-
duced. In the old code, the first of these was given
by the signalman at the sending end holding the
needles to "Train on line" during the time the
signalman at the receiving end pegged the handle
at his own end to do the same. The introduction
of these signals has resulted in the discontinuance
of this method. Three dial signals replace two
formerly used in connection with shunting, the
difference in the number arising from the distinction,
RAILWAY SIGNALLING. 73
made between passenger trains and others, a distinc-
tion not recognised by the shunting signals of the
older code.
The regulations for guidance in the use of the
1896 code call for no special comment other than is
involved in directing attention to the clear and precise
language used in describing the method of signalling,
the definition of the limits of the section, and the
difference of practice to be observed in offering the
" Is line clear " signal when the section is already
occupied, where passenger trains are or are not
involved.
Block Indicators. — Besides the system of signal-
ling already alluded to, which consists of train-
distinguishing or train-position signals, and which
are invariably given by a bell code, electrical block
instruments of another class perform the equally
important duty of indicating at all times the actual
condition of the line, whilst the bell signalling of
trains may be said, generally, to deal with the marshal-
ling of traffic and notification of its progress through
the several stages incidental to the usual working.
The indicators, of whatever form, are a reminder at
all times of the stage that has been reached, and
are therefore entirely connected with the safety of
the operations.
Examples of the earlier forms of indicator, taken
from the illustrations accompanying the report in
the " Proceedings of the Institution of Civil Engi-
neers " of Mr. Preece's 1863 paper are given by Figs,
i to 7.
A brief analysis of the various conditions of the
74
RAILWAY SIGNALLING.
-line and the indications required from block indicators
:may be useful.
FIG, i. — Cooke and Wheatstone's Indicator.
Theoretically, there are only two conditions of the
'line — line occupied by train, and line clear of trains.
Practically, the exigencies of traffic demand the pre-
PHSSEAICER TRAIN GOODS AND /V1IN E RALTRAIN
NOrUNDERSTAND B-E READY TRA/MNOTOUT BE READY
NOT UNDERSTAND BE READY TRAIN NOftHJT BE READY
LINE
BLOCKED
AT AAV
STATION
LINE LINE
BLOCKED CLEAR
ATMY AT MY
STATION STATION
FIG. 2. — Great Northern Railway Indicator.
paration of a section some time in advance of the
actual entry of the train into the section in order to
obviate the delay that would otherwise take place.
RAILWAY SIGNALLING,
75
Jtt.
FIG. 3. — Regnault's
Indicator.
J
HARROW BUSHEY
FIG. 4. — London and North- Western
Railway Indicator.
FIG. 5.— Tyers' Indicator.
76
RAILWAY SIGNALLING.
If block indicators shall be required to show the
condition of the line at all times, these must be
provided with some means of showing an indication
which shall differ from " Train on line," or any other
indication as completely as the state of preparation
differs from the conditions indicated by the " Train
on line," or other indication.
A study of the code given on pages 48 to 50, together
with the regulations framed for working it, shows
that the indication exhibited by pegging to "Line
U P DOWN
HEAR CLOSED
V
1LEAR CL03LD
V
FIG. 6. — Bartholomew's Indicator.
clear " is intended to show an intermediate stage
between " Line blocked " and " Train on line."
The indication intimates the readiness of the signal-
man at the receiving end of the section to accept a
train of the character indicated by the particular form
of " Is line clear " signal sent, which is known to
be approaching the point of entrance to the section ;
and it further intimates that no operations involving
the occupation of the line represented, by any other
train than that signalled, will be undertaken at the
receiving end of the section. This indication is not
RAILWAY SIGNALLING.
77
cancellable by the signalman at the receiving end of
the section for his own purposes, except for the most
exceptional occurrences outside his control. On the
SIGNAL
ON v OFF
FIG. 7. — Mr. Preece's Apparatus.
other hand, cancellation of the indication may be
obtained by the signalman at the sending end of
the section, but only by the concurrence of the
78 RAILWAY SIGNALLING.
receiving signalman, who controls all the indications
exhibited. Hence, " Line clear " is a positive indica-
tion of the most important character, and shows a<
stage of working to which neither "Train on line"
or " Line blocked " is applicable. The continuous
indication is a reminder to the signalmen at either
end of the last stage of the operations performed
by them jointly.
If we consider the indication next in order, " Train
on line," we find that it is a subsidiary indication,
more of the nature of an intimation of the progress of
the train than of any other character ; and signifies,
generally, that the train is under the control of the
signalman at the receiving end of the section, and
that he is aware of the necessity for taking steps to
deal with it as its character, as given by the dis-
tinguishing signals, demands. To the signalman who
has dispatched the train, as well as the signalman
who is to deal with it during its further progress,
the continuous indication exhibited intimates simply
the occupation o£ the line by a train and its passage
beyond a certain point. Practically, then, the " Train
on line " indication is simply the complement of the
" Line clear," and intimates merely a change of
position on the part of the train.
The next indication in order is " Line blocked."
This is the normal position of the indicating needle
after the " Train out of section " signal has been
given and acknowledged. This indication is a most
important one, and a reference to the regulations
will show that, under normal conditions of working,,
the intimation conveyed is " Line clear of trains, but
RAILWAY SIGNALLING. 79..
blocked until permission is given for further traffic."
From this we see that the ruling principle of block
working is the asking and receiving permission to
forward traffic before its dispatch from any point.
Further consideration of the code and regulations
shows that the "Train on line" indication is made
to do duty on other occasions than those of the
simple passage of trains from one end of the section
to the other. The "Blocking back" signals are an
instance of this use of the " Train on line " indication.
Careful examination shows that the intimation con-
veyed under such circumstances is not essentially
different from that conveyed in the case previously
considered. In both cases the indication shows the
presence of a train between the two block stations
concerned, in such a position as does not warrant
the " Line blocked " indication being exhibited.
Relative Importance of Indications. — Considera-
tion of the relative importance of the three indications,
"Line clear," "Train on line," and " Line blocked,"
shows the first to be the most important, since it is*
the only indication which must be secured before
action is taken to dispatch a train. Under normal
circumstances of working, we find that before " Line
clear " can be given for a train, the previous train
must have reached points on the line which are-
defined with some precision in the regulations. The
limitations on the exhibition of "Line clear" for
trains which have to approach fouling points at
junctions, show the importance attached to the
indication ; and the restrictions under which the
" Is line clear " signal may be offered to the
8O RAILWAY SIGNALLING.
advance station before the previous train has been
signalled out of the section, shows how the possibilities
that may arise in connection with irregular working
are recognised.
It will be noticed that a distinction is drawn
between signals and indications ; and the distinction
is a most necessary one. By indications, is meant
the more or less permanent intimations conveyed by
the position of the block indicators of the condition
of the line for the time being ; by signals, is meant
the transient intimations, given either on the bell or
indicating apparatus, which relate to other matters
than the condition of the line. It seems necessary
to call attention to this distinction, since there seems
to be a tendency in some quarters to confuse the
two classes by substituting "Train entering section"
for "Train on line," as the title of one of the indi-
cations of the condition of the line. " Train entering
section " is not so clearly indicative of what is intended
to be conveyed by the permanent deflection of the
needle as " Train on line." The entrance of a train
into a section cannot well be considered as being
continued during the whole time the train is passing
through the section. Entrance into a section is
complete when the signal controlling such entrance
has been put to "Danger" behind the train; and
the intimation of the performance of the operation
should be of the nature of a signal, as here distin-
guished from an indication. It is desirable in all
cases that the title of an indication or a signal
should, in the fullest manner, indicate the nature
of the operation. "Train on line" is more nearly
RAILWAY SIGNALLING. 8l
representative of the actual condition of things
during the passage of a train through a section
than " Train entering section," which represents a
merely momentary operation.
The cancellation of signals, or of indications being
exhibited as the result of previous exchange of
signals, is a question of considerable importance.
Cancellation becomes necessary at junctions where,
through misapprehension, the wrong line has been
prepared for an approaching train ; and at other
places from various causes, such as its being found
necessary to shunt a train for one of greater
importance to pass. A study of the regulations to
be observed will show that, theoretically at least,
cancellation should only be necessary in the case of
a " Line clear " indication being exhibited. Cancel-
lation of a " Train on line " indication ought never
to be necessary, since the preceding "Train entering
section " is not supposed to be sent until the train
is leaving the block station at the entrance to the
section ; and the " Train on line " indication indi-
cates the completion of the operations sanctioned
by the exhibition of the preceding "Line clear"
indication.
Form of Instrument. — At one time considerable
discussion centred on the most suitable form of
instrument for indicating the condition of the line.
Some inventors pinned their faith to instruments in
which the indicator was a small semaphore arm, or
a facsimile in miniature of the outdoor mechanical
signal, and argued that the train - distinguishing
signalling apparatus should be of a different character
6
82 RAILWAY SIGNALLING.
to the indicating apparatus, but not necessarily a
separate instrument, since they served distinct
purposes, and that uniformity in design of the
mechanical signals and the block indicator was
desirable in many respects. Others, again, preferred
some form of the " needle " instrument, so familiar
on railways, and contended that the indication was
in any case arbitrary, and, consequently, when once
established and understood the character of the
indication was immaterial. It was further contended
by the advocates of the single-needle instrument that
it allowed a greater variety of signals to be sent, and
that it also possessed the further advantage of cheapness.
Intimately connected with the most suitable
character of block indicator is another point which
seems to have been considered of some importance
by inventors of block apparatus, and upon which
much ingenuity has been exercised. This is the
reduction of the number of line wires to one ; and
the ability to perform all the operations required
for double-line block working by one line wire, is
still often urged as a recommendation on the score
of smaller cost for erection of wires and their
maintenance.
Roughly, instruments for block working may be
placed in one of two divisions. In the first, the
indicating apparatus is stable in either of the positions
it can take up, the current is transient, and is only
used to effect a change of position. In the other
division, the indicating apparatus is stable in one
position only, and change of position from the normal
can only be maintained by a continuous current.
RAILWAY SIGNALLING. 83
An example of instruments of the first division
may be seen in the block instrument invented
by the late C. V. Walker (Fig. 8), which was at
one time in general use on the old Stockton and
Darlington Railway, now a division of the North-
Eastern Railway, and is still to a limited extent.
J I
FIG. 8.— Walker's Block Indi-
cator, One Wire.
FIG. 9.— Single-Needle Block
Indicator, Three Wires.
This instrument was also in use on the South- Eastern
Railway, of which Mr. Walker was at one time the
electrical engineer. A further example of this class
of instrument, but of different construction, is the
one-wire needle instrument of Tyers (Fig. 10) now
in use on the London and North- Western Railway.
6*
84
RAILWAY SIGNALLING.
Examples of instruments of the second division1
are furnished by the single-needle three-wire block
instruments in use on the North-Eastern, Great
Northern, Midland, London and North- Western, and
other railways (Fig. g).
Instruments of the first division indicate two con-
ditions of the line only — viz., "Line clear" and " Line
blocked," or "Train on line." Instruments of the
second division indicate three conditions of the line —
FIG. 9A. — Spagnoletti's Indicator,
viz., "Line blocked" (the normal position), "Line
clear," and "Train on line." The difference just
shown may seem to be of minor consequence, but it
is, in reality, of the first importance to the proper
indication of the exact position of affairs at any
stage of block working. " Line clear," with instru-
ments of the first division, indicates that there is no
train in the section of line to Which the instrument
refers. With instruments of the second division,.
RAILWAY SIGNALLING. 85
however, it not only indicates that there is no train
in the section, but also that the signalman at the
receiving end has given permission for a train to be
sent forward, and has made preparations for its arrival.
As an illustration of the difference in working with
the different classes of instruments, the following
UP TRAIN UP ONE
ON LINE CLEAR
DOW* TRAIN OOttNUNE
ONLINE CLEAR
FIG. 10. — Tyers' Block Indi-
cator, One Wire.
FIG. n. — Preece's Block Indi-
cator, One Wire.
extracts from the regulations setting forth the
methods of working are given :
" Prior to the dispatch of a train from A, the
signalman there, provided he has received the
4 Train out of section : signal for the previous train,
and the block indicator is in its normal osition,
86
RAILWAY SIGNALLING.
must call the attention of B, and having obtained
it, must give the proper ' Is line clear ' signal ; if
the line be clear at B, the signalman there must
acknowledge the signal by repeating it. The signalman
at A may then, if the line is clear, take off his
signals for the train to leave A.
" On the train leaving A, the signalman there must
FIG. 12. — Hodgson's Block Indicator (Saxby and Farmer's Lock and
Block), One Wire.
send the ' Train entering section' signal to B, and I
the signalman at B must acknowledge the signal by
placing the block indicator to ' Train on line/ "
" Prior to the dispatch of a train . . . from
A, the signalman there, provided he has received
the ' Train out of section ' signal for the previous
train, and the block indicator be in its normal.
RAILWAY SIGNALLING. 87
position, must call the attention of B, and, having
obtained it, must give the proper ' Is line clear '
signal ; if the line be clear at B, the signalman there <
must acknowledge the signal and peg the block indicator
to the ' Line clear position.' The signalman at A may
then, if the line is clear, take off his signals for the
train to leave A. On the train leaving A the signal-
man there must send the * Train entering section '
signal to B, and the signalman at B must acknow-
ledge the signal and peg the block indicator to
* Train on line.' "
Mode of Working. — The first of these quotations
represents the mode of working a single-wire system
with instruments of the first division. In this case
the signalman at the sending end has nothing to
remind him that he has, or has not, obtained permission
to send a train forward to the advance cabin, and
the signalman at the receiving end has nothing to
remind him that he has given, or not given, such
permission. In both cases the signalmen have to
rely on their memories, or their booking, for reminders
of the " Is line clear " signals that have passed
between them.
The second quotation is for a three-wire system,
with indicating instruments of the second division.
In this case the " Is line clear " signal, and its
acceptance by the signalman at the advance cabin,
is recorded at both ends of the section until the
permission has been acted upon, and the " Line
clear" indication is superseded by "Train on line."
With either class of instrument the line is con-
sidered " blocked " until permission is given by
88 RAILWAY SIGNALLING.
acknowledging, by repetition, the "Is line clear"
bell signal, but the fundamental difference between
the two modes of working is the ability, with
instruments of the second division, to record the
acceptance of the " Is line clear " signal, so that
the signalmen at both ends can, from the indications
of their respective instruments, obtain reminders of
the signals that have passed, and the position of
the line at any time. Obviously, the condition of
a section cannot be the same after permission has
been given to forward a train as before that per-
mission was given, even if the train has not actually
entered the section. The acceptance of the pre-
liminary " Is line clear " signal indicates that the
line is clear to the advance cabin, that previous
trains are fully protected by signals, and that no
operations involving the fouling of the line will be
undertaken at the advance cabin until the train
accepted is clear. Hence, it would appear that
instruments of the first division fail to take cognisance
of what is without doubt an important condition of
the line. How important it is that the operations of
the two signalmen, who must necessarily co-operate
in the working of traffic, should be perfectly syn-
chronised, need not further be commented upon.
Generally, it may be said that instruments which
require only one line wire for all the operations
involved in double-line block working are those which
use transient currents only, whether employed as
train-distinguishing signals or as indicators, since the
line may be required for the former signals whilst
the instruments are indicating " Train on line "
RAILWAY SIGNALLING.
89
for one or other of the lines of rails for which it
is used. Conversely, it may be said that instruments
which require continuous currents for the maintenance
of their indications are those which will require three
wires, since the indicators must work independently
of each other and of the bell-signalling apparatus.
E.E.
FIG. 13. — Winter's Block Indicator (Siemens).
From what has been said it follows that the number
'Of independent batteries required will be less for
instruments of the first division than for those of
the second division, since under actual conditions of
work currents are not likely to be used in any one
'cabin in both directions simultaneously. Where
90 RAILWAY SIGNALLING.
transient currents are used only, the number of
batteries required may be reduced to the number of
operations that may be carried on simultaneously.
With instruments using continuous currents for main-
taining the necessary indications, the number of
independent batteries required will necessarily be
greater owing to the greater number of operations
which may require to be carried on at the same time.
It would therefore appear that block instruments
using transient currents, and requiring not only one
line wire but a smaller number of independent
batteries, would be preferable considered from an
economical standpoint. Against this advantage it is
urged that cutting down the line wire to one, and
reducing the battery power to an absolute minimum,
is an operation of the nature of putting too many
eggs in one basket. If a fault occurs on the line
wire, both lines of rails are affected, and must be
worked at " Caution " until the defect is removed.
If the telegraph lineman is not immediately available,
the disorganisation of traffic may be considerable.
On the other hand, with instruments of the second
division, a failure of one line wire affects that instru-
ment and the line it represents alone, the other line
being worked as usual. It by no means follows that
the number of line faults on a three-wire block will
be three times that on a one-wire.
An important point in connection with the class
of instrument most suitable for block working is the
indication the apparatus will give when, through a
defect, the instruments are not available for use.
With instruments of the first division the indication
RAILWAY SIGNALLING. QI
will remain in the position it happened to occupy at
the time the defect occurred. This may be either
" Line clear " or " Line blocked," according to the
condition of the line at the time. With instruments
of the second division, where any indication other
than "Line blocked" is only maintained by the use
of a continuous current, a defect of the line wire or
battery will at once cause the indicators to show
" Line blocked."
When a defect arises in the block apparatus for
any section, involving the suspension of block working,,
the ordinary space limit is replaced by a time limit,,
and every train which is sent through that section -
must be first brought to a stand and the officials im
charge of the train advised of the breakdown and
instructed to proceed cautiously. Practically, the
section of the line where the failure exists is treated
as if blocked on the approach of any train which may
require to pass through that section. With instru-
ments of the first division the indications of the
faulty block instruments may, or may not, correspond
with the theoretical condition of the line ; with
instruments of the second division, the defect ensures
the indications being such as will correspond with
the conditions under which the line is being worked.
Instruments of this class may therefore be fairly
considered as more reliable under the conditions
cited than those of the first division, and the
indicators have the further advantage of being self-
testing to a large extent when in use.
Disturbance of Instruments. — Instruments of the
second division are subject to a class of disturbance
92 RAILWAY SIGNALLING.
which does not affect those of the first division. In
consequence of the generally lighter construction and
greater sensitiveness of the former, they are affected
to a much greater degree by the presence of earth
currents or the occurrence of "magnetic storms."
Whilst the latter class of disturbance are of rare
occurrence and never for prolonged periods, the
former are nearly always present, and the selection
of an earthing point which will allow of the block
indicators keeping their normal position exactly is
frequently a puzzle of no mean order. Earths which
are made within a few yards of each other often give
quite different results, and combinations of different
earths will often give results which cannot be
obtained from any of them separately. Moreover,
there is no certainty that uniform results will be
obtained from any earth or combination of earths
which, on being first connected, are found to
work satisfactorily ; indeed, it is no uncommon
experience for them to change before the man
leaves the place.
At places where the earth connection has to be
made in rocky or sandy soils, the resistance to earth
is sometimes considerable, and " contact " between
the different instruments ensues. It is not always
possible to obviate this defect by utilising the rails
as the return, more especially during dry weather
and in places where junctions intervene. The remedy
for these defects is obvious, and consists in diminishing
the sensitiveness of the block indicators ; and since
" the movements of the block instruments and bells
must be made slowly and distinctly," there is no
RAILWAY SIGNALLING. Q-J:.
necessity for so great a degree of sensitiveness in
instruments for block working.
Cost and Maintenance. — The relative cost for
construction and maintenance of the three-wire
continuous-current and the one-wire transient-current
systems is a subject upon which, as has already been
stated, considerable emphasis has at different times
been laid. Where the instruments for use with
one line wire are not overweighted with patentees'
royalties there can be no doubt of the smaller cost
for construction, and, other things being equal, for
maintenance also. But it should not be forgotten
that a complete block section includes, besides the
electrical equipment, the lines themselves, the neces-
sary buildings, and the mechanical signals and points,
with their interlocking mechanism, and that, of these
items, the electrical is probably the least expensive.
Hence, the difference in the cost between a three- wire
and a one-wire system is likely to be an almost
inappreciable fraction of the total cost of the section,
and this is rendered still more apparent when it is
considered that the most expensive item of the elec-
trical equipment — the construction of the pole line —
is invariably used for other purposes than block
working proper.
Hence, whilst it may be said that block circuits
using one line wire and transient currents may be
somewhat cheaper to maintain than circuits requiring
three wires and continuous currents, yet the difference
is small, and its importance is discounted by the
greater variety of signals that may be used on the
latter without an unnecessarily intricate code ; the
94 RAILWAY SIGNALLING.
additional indication provided between the accept-
ance of the " Is line clear " signal and the " Train
entering section" signal; the greater certainty of
the indicators being in accordance with the condi-
tions under which the line is worked when a defect
exists in the block apparatus ; and the self-testing
character of the apparatus used.
Considerations for Choice of Instruments. — From
the foregoing it will be seen that the considerations
regulating the choice of block instruments are numerous
and of great importance. The first consideration is,
of course, their ability to provide a separate indication
for each of the conditions to which the line is liable.
The instruments must provide for the use of an
extensive code, without its being intricate or the
signals liable to misinterpretation. The indicating
instruments must not be liable to reversal or dis-
turbance from external causes. They should be self-
testing when in use, of simple construction, and not
liable to get out of order easily ; but whenever an}'
instrument, line, or battery fault develops, it should
result in the indicating instruments occupying posi-
tions in accordance with the conditions under which
traffic will be dealt with during the continuance of
the fault. Further, as will be seen from the remarks
on the cancellation of signals and indications, the
system, whatever it may be, must provide for this
being done, but it should only be done by the
concurrent action of the two signalmen concerned.
Besides these considerations, there is the question
of the independence of the two lines of rail con-
stituting any section of double line. This independence
RAILWAY SIGNALLING. 95
is complete in so far as the movements of traffic is
concerned, and any system of block working which
does not under any circumstances preserve this
independence is defective. Such a consideration as
is here adduced would limit block working to some
form of three-wire system, since, as we have already
seen, failure of the line wire of any single-wire
system involves both line of rails.
The extensive use of three-wire systems with some
form of single-needle instrument as the indicator,
involving the use of continuous currents for the
maintenance of the active indications, shows that this
form of instrument is much in favour with those
responsible for the recommendation of apparatus for
this purpose ; and the infrequency of breakdown due
to defects of apparatus justifies the choice. The
variety of signals that can be sent on three-wire
single-needle instruments is very great, and the instru-
ments are simple, cheap, and easily maintained. The
indications are maintained by continuous currents ;
the methods of working and the indications exhibited
are not easily mistaken ; and failure of line, battery,
or instrument results in the indication exhibited at
the sending end being in accordance with the con-
ditions under which subsequent trains are dealt with
until the defect is removed. The chief defect, which
in earlier days caused the needle instrument to be
regarded with suspicion, the reversal or demagnetisa-
tion of the needle, was removed by the adoption of
the induced needle, and the five or six pound magnet,
which at one time constituted an indispensable part
of the lineman's equipment, is now a thing of the past.
96 RAILWAY SIGNALLING.
It must be understood that these remarks are made
on a system of signalling which depends entirely upon
the man operating the instruments, attention having
hitherto been directed exclusively to non-automatic
systems. Instruments and appliances in which auto-
matic working is obtained in a greater or less degree
are described in the section devoted to instruments.
At the same time it is not admitted that the
requirements of indicators for automatic working
differ in any way from those required for non-auto-
matic working.
CHAPTER III.
TELEGRAPHING OF TRAINS — SIGNAL WHISTLES —
HEAD, TAIL, AND TRAIN SIGNALS.
In addition to the signalling of trains on the block
instruments as described, the signals for which, with
one exception, relate to the dealing with trains as they
arrive, the telegraph systems of railways are used as
important adjuncts to train signalling. Railway trains
of any class do not invariably run to their schedule
times throughout their journeys, in consequence of the
innumerable chances of delay involved in the conduct
of a large mixed traffic under all circumstances of
weather, and irregularities consequent upon delay in
receipt of traffic. Under such circumstances, traffic
on railways would soon be completely disorganised if
no other means of imparting information of the move-
ment of trains to those who have the control of various
portions of the line were provided. In order to meet
the irregular movements of trains, the times of
departure of the more important are telegraphed from
point to point, so that in the event of important trains
being delayed beyond their booked time, other traffic,
which otherwise would be kept waiting at some point
on the line for its passage, may be allowed to proceed
as far as possible on its journey as the time available,
and the facilities ahead for disposing of it, admit.
Train Messages. — These messages are of consider-
able importance, and rank second in the order of
7
98 RAILWAY SIGNALLING.
importance of railway messages, and constitute fifty-
five per cent, of the messages at certain important
telegraph centres. Inattention to the information con-
veyed by these messages, or neglect of attention to the
instrument when they are offered, whilst not likely to
be a source of danger under any but the most peculiar
combinations of circumstances, is likely to cause
unnecessary delay ; and as a consequence we find
from a copy of the instructions for telegraphing such
trains (given below) that the time allowed for non-
attention is limited.
INSTRUCTIONS FOR TELEGRAPHING THROUGH AND LOCAL PASSENGER
TRAINS.
1. All regular trains must be reported by their numbers as per
working time tables, and so entered on the train slips.
2. No train must be telegraphed from a station until the time of its
departure has been reported to the telegraph office by the stationmaster or
the person appointed by him to that duty. Such report must in no case
be made by the telegraph clerk, except in signal cabins, where the clerk
may do so at the request of the signalman, who must tell him the times
the trains leave.
3. Trains must be reported forward immediately after their departure
has been reported. Should the instrument be engaged with other
service, the station having a train to report will, after three minutes-
have elapsed from its departure, interrupt with the prefix M. T. D. G.
messages must not be interrupted with the M. T. prefix. If from any
cause trains are not reported, a report of the circumstance must be
forwarded the same day.
4. When two stations have a train to report at the same time on the
same instrument, each station must convert the time the train left into
a code, which must be exchanged between them, and preference given to
the one which left first.
5. After calling a station for three minutes unsuccessfully the clerk at the
sending station must call the next to which the train has to be reported,
and so on until it has been reported to all the others in order, after
which he must again call the station passed over.
6. Whenever a train cannot be telegraphed owing to the time of
RAILWAY SIGNALLING. gg
departure not having been reported, the telegraph clerk must within ten
minutes of the time it was due to leave report the circumstance to the
stationmaster.
7. In case information of the departure of any train, except those which
stop at all stations, shall not have been ^received within ten minutes
after the time at which it is due, the telegraph clerk or signalman may
ask for it. All other enquiries, except by message, are strictly prohibited.
8. All cases of non-reporting or delays, from whatever cause, as well
as every case of inattention to calling, exceeding three minutes, must be
reported by letter, in addition to a note of the irregularity being made upon
the train slips. To denote that the circumstance has been reported, the
letters "ex" must be written near the remark.
9. The "understand" signal must be given at the end of every word in
the train reports.
10. Mixed and slow trains are only to be signalled when running ten
minutes and upwards late. If, after receipt of such notice, it is found
they have made up or lost time, they must be signalled forward
accordingly.
Note. — The term "slow trains" applies to those trains which stop at
all stations on their journey. The term "mixed trains" applies to those
trains which stop at the majority of stations only.
n. Special and excursion trains, including special goods, cattle, etc.,
must be designated by the name of the station from and to which the
special is running.
12. All train reports must be entered on the respective train slips.
A.M. or P.M. must be inserted opposite each entry.
13. The names of all stations must be written in full on the train slips.
Those stations which receive trains that have to be retransmitted to them
must insert the name of the station the train left as well as the transmitting
station.
14. Stations must keep their train slips on hand twelve months.
The whole of a line is divided into districts accord-
ing to the run of the circuits, and the trains are tele-
graphed as per the general instructions given and the
special instructions provided for each district.
Telegraph circuits have, of course, other objects in
view, and their route and calling points are not always
such as is most desirable for the purpose of train
7*
100 RAILWAY SIGNALLING.
signalling ; and, in consequence, messages relating to
one train having frequently to be sent on more than
one circuit. Where important traffic is large and the
points to be informed of the movements of trains are
numerous, such messages as these are no doubt
responsible in a large measure for the congested
state of railway companies' telegraph lines in general ;
and in any case entail a large amount of work in
the detail arrangements to meet the requirements.
Much has been done to meet the difficulties
encountered by the provision of local cabin circuits,
but a revision of arrangements and circuits would
do much to increase the efficiency of this part of
railway signalling.
Use of Telephone.— The telephone, has, of course,
been largely adopted by railway companies, and one
of its uses is in the transmission of information from
point to point for the telegraphing of trains, and, as
might be expected, it is much more expeditious than
the telegraph. As with the telegraph, however, other
considerations have been taken into account in making
circuit arrangements, and, practically, much of the
experience which is available from consideration of the
defects observable in telegraphic arrangements is being
ignored in the provision of telephonic communication,
in that the latter are also being provided to suit purely
departmental purposes.
It should be said that M. T. messages, such as are
here referred to, are in no way connected with arrange-
ments for safety. The safety of trains depends
entirely upon the block signalling in so far as electrical
signalling is concerned or capable of affording safety
RAILWAY SIGNALLING. IOI
by its rules being adhered to. M. T. messages are
entirely concerned with the convenient marshalling of
traffic for rapid transit.
Complete System. — We have hitherto confined our
attention to the electrical signalling for the marshalling
and passage of traffic. Such signalling, however,
forms only a part of the whole system, and any
consideration of one part only must necessarily be
incomplete. The signalling not already alluded to
may be conveniently divided into two classes :
(a) Signals to the signalman from outside.
(6) Signals by the signalman to the outside.
The first class comprises the signal whistles provided
for intimating to the signalman the intention or desire
of the driver of an approaching train to proceed in
some particular direction or to some particular point
controlled by the signalman, and the head and tail
lights, head-boards, etc., which are used to distinguish
different classes of traffic from each other, and for
other purposes of a similar nature. As no two parts of
a railway are exact counterparts, the number of general
instructions for signal matters are a minimum, and for
one particular line are as given below.
SIGNAL WHISTLES TO BE GIVEN BY DRIVERS OF ENGINES WITH OR
WITHOUT TRAINS.
In reference to all junctions whether of main, branch, or independent
lines, and to all cross-over roads and sidings, not otherwise hereafter
specially provided for, the following general rules will apply :
102
RAILWAY SIGNALLING.
No. of Whistles.
Long.
Short. | Long.
JUNCTIONS.
For a train approaching a junction on a main or
continuous running line, and intended to proceed
beyond the junction on the same line....
For a train approaching a junction on a main or
continuous line, and intended to proceed beyond
the junction upon a branch or other line diverging
from the main or continuous line, or vice versa, . . .
STATIONS.
As an indication that a goods or mineral train
which is timed to stop has no wagons or goods
to leave, and will not stop unless required by
station ,
CROSS-OVER ROADS.
For permission to use a cross-over road between
main lines, or between the running lines of a
branch or independent line, and after using the
cross-over road, as an indication that the engine
or train is clear of the points
SIDINGS.
For permission to enter a siding, and as an indica-
tion that the train is clear of the points, and ready
to enter
As an indication that the whole of the train has
entered the siding, and is clear of the safety points
For permission to return from a siding to the main
line, and as an indication that the engine or first
vehicle is within the safety points and ready to
leave
As an indication that the whole of the train has left
the siding, and is clear of the points
2 i
I crow
The signal whistles for particular places are very
numerous, and entail careful arrangement, as will be
evident when it is stated that for the line referred to
the details cover over one thousand eight hundred
and fifty different signals, the greatest consecutive
RAILWAY SIGNALLING. 103
number at any place to form a signal being six. Of
-course many of these are repetitions, but the number
gives some idea of the minuteness with which the
details have to be worked out.
Head Lights, — The head lights or boards and the
tail lights or lamps of trains are important signals
transmitted to the signalman, and advise him in the
case of the head lights or boards of the character of
the traffic he is dealing with, and in the case of the
ordinary tail lamp that the train is whole. The objects
of the two divisions are of course entirely different.
Whilst the latter is a necessity if safety is to be
assured, the former serves the subsidiary but still
important function of indicating the relative import-
ance of trains.
The head-boards carried on the engines by day differ
in shape and colour, and the intimation conveyed varies
with their position on the engine also. The shapes
vary between circular, elliptical, rectangular, and
rhombic ; the colours are generally white or green,
whilst the positions are at the foot of the engine
chimney on one or both sides of the smoke-box, or in
the middle, and in some cases in all these positions.
Every line has its own combinations for indicating the
character of trains in this way. Examples of these are
given below :
Every engine, except as specified under this heading,
must have a white light fixed on the right-hand
side of the buffer beam, thus :
104
RAILWAY SIGNALLING.
Engines of fast pas- ^
senger trains, fish I Two white lights — one over each
trains, and break- [ buffer, thus :
down van trains... I
Engines of slow
senger trains
light trains
arpas-^
is and
A white light
buffer, thus :
left-hand
Engines of express
goods and through
trains of cattle,
perishables, and ship-
ment traffic
' A white diamond board at
bottom of engine chimney
during day, and one green
light over right-hand buffer
and one white light over left-
hand buffer at night, thus :
Engines of fast goods
trains not having to
stop at intermediate
stations and sidings..
A white diamond board over
left-hand buffer of engine
during day, and two green
lights, one over each buffer,
at night, thus :
"SET
and ballast trains
over left-hand
buffer, thus :
Engines of fast pas- \ One white light at foot of
senger trains / chimney, thus :
RAILWAY SIGNALLING.
105-
Engines of slow pas
senger trains
light engines
pas-'j
and -
• ••••-« J
One white light on right-hand
side of smoke- box, thus :
Engines of most
important goods
trains, including
fish, fruit, yeast,
and cattle trains...
One white light at foot of
chimney, one white light on
right-hand side of smoke-box,
and one green light on left-
hand side of smoke-box, thus :
Engines of express j
goods trains ...... |
V
white light on right-hand
side of smoke-box and one
green light on left-hand side
of smoke-box, thus :
Engines of passenger \One white light on each side of
trains / buffer beam, thus:
side
RAILWAY SIGNALLING.
Engines of slow or \One green light on right-hand
pick-up goods / side of buffer beam, thus :
Tail Indicators. — " Train following boards " are
attached by day to the last vehicle of a train when
circumstances render it necessary for another, of the
character of a "special," to follow immediately after.
At night an additional tail lamp is added in such a
position as will prevent its being confused with the
ordinary tail lamp or " Last vehicle " signal, which
is usually fixed to the lower framework of the last
vehicle.
Other special arrangements of side and tail lamps
are necessary where more than one pair of running
lines are in use, and an arrangement of lamps for the
purpose of enabling drivers to distinguish trains on
their own line from trains on a line parallel to theirs,
the direction of trains on both being the same, as
shown below.
TRAIN TAIL AND SIDE LAMPS.
To enable drivers to know whether a train in front of them is on the line
on which they are running or on the line parallel with it, the following
arrangement of train tail and side lamps must be carried out on those
portions of the railway where there are other running lines besides the up
and down passenger lines :
I. Trains running on the passenger lines must
<carry three lamps in a triangle, thus :
RAILWAY SIGNALLING.
2. The signal to indicate that a special is following
on the passenger lines must be shown by an addi-
tional lamp being placed at the bottom of the last
vehicle, thus:
3. Trains running on the goods lines must carry
three lamps in a straight line, thus :
4. The signal to indicate that a special is following
on the goods lines must be shown by an additional
lamp being placed at the bottom of the last vehicle,
thus:
The tail lamps must be carried in their proper positions by day as well
as by night.
The signal lamps indicating " slip " carriages are
another important example of the class of signals
exhibited to the signalman from outside.
A method of distinguishing a train which carries a
slip carriage is shown below.
108 RAILWAY SIGNALLING.
The two tail lamps carried are arranged in a
vertical line, and upon the presence or absence of
these lamps on the last vehicle of trains which
signalmen know are intended to carry slip carriages,
depends the action that must be taken by signalmen,
as thus —
13. Should a train that is appointed to convey a
slip carriage pass a station or cabin showing wrong
tail lamps, the signalman in the first signal box which
the train passes (unless it be the box immediately
preceding a slip station, for instructions as to which
see Rule 14) must conclude that the slip carriage
has become detached, and must signal to the next
signal box ahead "to stop and examine train"; and
if the signalman at that box finds on the arrival of
the train that the slip carriage has broken away, he
must telegraph on to the next box, "Slip carriage
broken away, train gone on without it," which message
must be repeated from box to box as the train passes
as far as the slip carriage would have run, the
train itself being signalled and the line cleared in the
usual way. If when the signal " Stop and examine
train " is given the train has passed the signal cabin
in advance, the signalman in that cabin must instantly
repeat this signal to the next signal box, and the
signalman there must stop the train, and act as
shown in preceding paragraph. Should the slip
carriage be afterwards sent on by special engine, it
must be signalled as if it were another or special train.
14. Should a train that has a slip carriage on pass
the station or cabin immediately preceding the station
at which the carriage is to be slipped showing wrong tail
RAILWAY SIGNALLING. IOQ
lamps, the signalman must not send on to the station
at which the carriage is to be slipped the sigmal
" Stop and examine train" but must keep the block
on and send the " caution " signal to the station in
the rear, and then ask the station at which the
carriage should be slipped, "Has slip carriage with
signals arrived?" If the reply is, "Slip carriage with
signals lias arrived" he must immediately clear the
line to the station in the rear, but if the answer is
"No" he must immediately telegraph to the station
in the rear " Slip carriage has broken away." Should
the train pass the station or cabin showing no tail
lamp, the signal " Stop and examine train " must be
sent to the station at which the carriage should be
slipped in the usual manner.
VISUAL AND AURAL OUTDOOR SIGNALS.
Of equal importance to the different classes of
signals already enumerated are those exhibited by,
or on behalf of, the signalman, for the guidance of
the drivers of trains. All other apparatus used in
railway signalling have this object in view, and are
simply means by which the signalman is kept informed
of the necessity or desirability of exhibiting certain
signals for the guidance of drivers of trains.
Such signals are of different kinds and of different
degrees of importance ; they are mainly visual signals
depending upon differences in material, shape, colour,
and position, but under certain circumstances aural
signals are substituted for the visual. Such signals
may be temporary hand signals exhibited from the
110 RAILWAY SIGNALLING.
signal cabin, or they may be fixed signals actuated^
at a distance from the cabin.
Hand Signals. — Dismissing the signals which are
made by holding the hands and arms in different
positions, we may start with the temporary hand
signals which are exhibited by signalmen under
certain conditions. These may be made by the use
of different coloured flags in the daytime, and by
different coloured hand-lamps at night. The practice
on different lines in the use of colours for signalling
purposes varies to some extent ; but in nearly all
cases the " danger " signal when exhibited by a colour
is red ; green is a " caution " signal, and white is an
" all right " signal. The purposes for which flags
and hand-lamps are used as signals are various, and
their uses are set forth in their proper positions in
the extracts from " General Regulations " relating to
signals given further on. Generally, it may be
said that hand signals are used in cases where the
use of the fixed signals is liable to lead to an incorrect
interpretation. Hand signals are therefore subsidiary
signals, made use of for exceptional circumstances.
Fixed Signals. — The fixed signals are usually placed
on posts at such a height and in such positions as
careful examinations of the line indicate as most suit-
able. The first necessity is that it shall be clearly
visible to the driver of an approaching train, at such
a distance as will allow him to act upon its indication.
The greater the distance at which the signal can be
clearly made out, the more time the driver has to act
upon it. At the same time there is a limit to this
when, in order that the signal may be seen at a con-
RAILWAY SIGNALLING. Ill
siderable distance under normal conditions of weather,
the signal arm is so high or the post placed at such
a distance from the running line that drivers have
difficulty in seeing the position of the arm or the
colour of the light exhibited during such conditions as-
obtain during a heavy fog.
The signals are usually of the semaphore pattern,
and the indications are given by the position of the
arm during the day and by the colour of the light
shown at night. The number of indications shown by
the positions of the arm are generally two — " danger "
and "all right," or "danger" and "caution." During
the day the " danger " signal is indicated by the
horizontal position of the arm, or the "all right"
or the " caution " signal, as the case may be, by the
arm being more or less inclined towards the post. At
night the " danger" signal is exhibited by a red light,
caused by a spectacle of red glass covering the front
of the lamp, and the " all right " or the " caution "
signal is exhibited by a green or white light in the
same way, the spectacles moving with the arm and
showing the signals corresponding to the position of
the arm.
The normal position of all fixed signals of the
semaphore type is at " danger," and the arrangements
are such that most defects, to which the means of
actuating such signals are liable, result in the signal
being placed to " danger." One important exception
should be noted. The contraction of the wire used
to actuate the signal by decreased temperature, tends
to pull the signal arm towards the " all right" position.
Many attempts have been made to compensate for
112 RAILWAY SIGNALLING.
this, and for the expansion of the wire due to increase
of temperature, with but little result so far. The
majority of signal wires are still adjusted by hand,
when the signalman observes that it is necessary,
either from the signal arm failing to drop to "off"
or return to " on " completely.
The green light used as the all right signal is
preferable to a white light for that purpose, in
that damage to a red spectacle would cause an " all
right " signal to be exhibited when the arm was at
"danger," and for certain signals the signalman would
have no means of knowing that any but the right
signal was being exhibited. Where red and green lights
are used for the "danger" and "all right" signals
respectively, the exhibition of a white light where
either of those should be seen is treated as a "danger"
signal. Incidentally it may be noted that green as
an " all right " signal is displacing white for other
methods of signalling than those under consideration.
At one time the exhibition of a white light by the
guard of a train to the driver indicated " all right."
Such a signal was almost universally used by guards to
intimate to the driver that all was ready for a train to
start from a station, say. Owing to the liability of the
driver to mistake a light carried by another person for
the signal he was expecting, a green light has been
substituted for this signal. Generally, it may be said
that where a light is required as a signal for a special
purpose, it should be so distinctive as to prevent its
being confused with a light used for any other purpose
where both are likely to be in operation at the same
place at the same time.
RAILWAY SIGNALLING. 113
In addition to the semaphore signals, ground discs,
so called, are used, generally in places where it is
inadvisable, owing to want of room or similar causes,
to erect the usual semaphore posts. Such discs are
not used as signals for main-line running, but for
sidings, cross-over roads, etc., where the traffic they
control is never in rapid motion.
Fixed signals are divided into " distant," " home,"
•" starting," " advanced starting," or, more shortly,
" advance," siding, and " calling on " signals. Dis-
tant signals, as their name implies, are fixed at
considerable distances from the signal cabin, the
distance varying from one thousand yards, or more on
occasion, to a few hundred yards where the block
sections are short. A glance at the rules to be observed
in connection with " distant " signals will show that,
although its movements are similar, one of the indica-
tions at least differs from that conveyed by other signals
when in the same position, in that it does not mark
the limit that must not be passed by a train. The
" distant " signal is the first signal that a driver sees
belonging to the signal cabin he is approaching, and
its indication is a preliminary notice to him of the
condition of things at the signal station from which
the "distant" is controlled. The " distant " is not
a " stop " signal, but may be passed if the driver is
assured that, notwithstanding the signal exhibited, the
line is clear to a certain point. He must, however,
-according to rule be prepared to stop at the signal
if necessary, or at any subsequent point between it
and the next signal.
On the other hand, there are reasons why drivers
8
114 RAILWAY SIGNALLING.
of trains should not assume that, because the " distant "'
signal is " off," the following signals are also in the
same position, notwithstanding the usual arrangement
of the lever interlocking. Each signal of a section
should be observed independently of any of the others ;
even a " distant " signal, when indicating " all right,"
should only be considered as referring to the portion of
line between it and the next signal in order of progres-
sion. The "distant" signal is a most important signal
for main-line work — not necessarily for that alone —
where fast traffic is great ; and affords drivers of such,
and other trains, evidence of the condition of the
station, intermediate cabin, or junction, in ample
time to draw up at the first stop signal in advance
if necessary. At one time, trains approaching a
junction on the divergent line had only one distant
signal to guide them, and were therefore in doubt,
until the home signals came into view, whether the
road prepared for them was that upon which they
wished to go. The usual practice is now to provide as
many "distant" signals as there are home signals, or,
practically, as many as there are divergent roads at the
junction. By this means the doubt and uncertainty
has been removed.
" Home," " starting," " advance " and siding signals
are of a different class, in that they are " stop " signals,
and mark the limit of advance for the time, unless
supplemented by other signals of an authorised nature.
" Home " signals are usually set as close as prac-
ticable to the cabin from which they are controlled,
and so as to protect the entrance to sidings, junctions,
and cross-over roads, so that shunting operations are
RAILWAY SIGNALLING. 115
carried out under the immediate observation of the
signalman and within his control. Consideration of
the rules relating to " home " signals shows that there
are occasions when these signals are passed when at
" danger," but on these occasions the indication
exhibited is superseded by authorised hand signals,
or their substitute, the "calling-on" signal. It is
worthy of note that these signals only take effect
after the " home " signal has practically done its
work by bringing the train to a stand, or nearly so,
It will be noticed that a train standing at a " home"
signal is not under the protection of any "stop"
signal belonging to the signal station from which
the home signal is actuated ; and the only protection
to such a train, beyond the cautionary signal of the
"distant," is that'afforded by the signals of the rear
cabin. Home signals are, of course, provided for
each of the divergent lines at a junction, all such
signals being generally upon one post in the order
laid down in the general regulations. Similarly, all
convergent lines are provided with " home " signals
fixed in such positions that trains, when standing at
them, do not foul either of the other converging
lines.
" Calling-on " signals, as will be gathered from the
preceding remarks, are merely an adjunct to the
" home " signal, and are intended to obviate the
difficulties often found in busy places to be attendant
upon the use of hand signals. With these signals
the liability to error from the hand signal not being
seen, or to its being taken as a signal by another
train, is obviated. Its use, however, is dependent
Il6 RAILWAY SIGNALLING.
upon the non-operation of the "home" signal, and
in all cases it is a " caution " signal.
Attention is called to the different conditions under
which trains are allowed to pass " home " signals
at junctions where starting signals are in use ; at
places other than junctions where starting signals are
in use ; and at places other than junctions where
starting signals are not provided. In the first case,
the "home" signal can only be superseded by a
" calling-on " signal. If the latter is not provided,
the " home '' signal must not be passed at " danger "
under any circumstances. In the second case, the
" home " signal must only be passed by lowering
the " calling-on " signal, or by a train or engine
which, for special purposes, are running in the
opposite direction to that for which the line is
intended.
In the third case, the driver obeys the " calling-on "
signal or the hand signal, but only to draw his train
witkin the protection of the home signal.
" Starting " or " advance " signals, when either is
used alone, represent the last point at which any
signalman has control over trains. Such signals
mark the end of one block section and the beginning
of the next, and they are proportionally important,
since any train once past such signal is out of the
control of the signalman. Hence we find that great
attention has been paid to this signal in systems of
working which have an automatic or semi-automatic
basis, and generally the control of it, but not neces-
sarily all the working, is vested in the signalman at
the cabin in advance, and becomes practically the
UNIVERSITY
RAILWAY
first signal for that section, or a duplicate " distant "
of a slightly different character.
"Starting" signals and "advanced" starting signals
may be both used at the same block station, or either
may be used alone as circumstances may require.
Where both are used, the first is generally a " stop "
signal for a particular purpose, such as that exhibited
to stop a passenger train at the platform of a roadside
station, or for controlling the exit of trains from
different points at more important points. Under
such circumstances the " advance " signal becomes
the signal controlling the entrance of the train into
the next section, and the " starting " signal only
allows the passage of the train to the next or
" advance " signal.
Of " siding " signals, whether semaphore or ground
discs, nothing particular can be said. They are
" stop " signals for local purposes connected with
the marshalling and distribution of traffic.
Fog Signalling:. — Consideration of the extracts
given from the general rules for outdoor signalling
shows that occasions arise when the outdoor visual
signals are replaced by aural signals owing to circum-
stances causing the former to become invisible. It
will also be gathered from the regulations respecting
fog signalling that the men employed for this purpose
are at other times engaged in other work, and must
be specially called for fog signalling as occasion
requires. The duty of calling out these men devolves
nominally upon the stationmaster for such places as
he is in charge of, but practically depends upon the
signalman, who has to decide when it is necessary to
Il8 RAILWAY SIGNALLING.
supersede the usual form of signalling to drivers of
trains. This responsibility is no light one, since much
depends upon the necessity being promptly met.
Fogs are not all of the same character, and they do
not as a rule give previous notice of their appearance
or of their probable duration. A fog may be a ground
fog, which obscures sight at a distance of a few feet
from the ground only, and signals may be quite visible
from the driver's elevation whilst the line itself may be
invisible to him. On the other hand, the fog may be
such as to totally obscure sight of objects at any of
the heights at which signals are placed generally.
Whilst there is this difference in the character of fogs
it is no unusual occurrence for a ground fog to change
to one of a more serious character, nor is it unusual
for a fog which threatened to be serious to suddenly
disappear, and thus obviate the necessity for the
special form of signalling. Under such circumstances
the responsibility for calling out men is likely to be
somewhat onerous. If the men are not called out
promptly, considerable delay will be inevitable if the
fog becomes serious, if nothing worse occurs. On the
other hand, if the fog is of a mild character, or
disappears quickly, the necessity for the fog-signallers'
services will have, in all probability, ceased before they
commenced work.
If the fog occurs at night, when it is more than
usually dangerous, the length of time that may elapse
between calling out the fog-signalmen and their
actually commencing work may be considerable, since
messengers must necessarily be sent to their homes to
call them out. Under such circumstances the change
RAILWAY SIGNALLING.
in the character of the signalling is not likely in all
cases to be so prompt as is desirable. It is true that
the regulations provide for fog signals being placed
on the lines opposite the cabin " when practicable "
during the time between calling out the fog-signalmen
and their arrival. This is not in all cases practicable,
and, even when done, it should not be forgotten that
the train which explodes the detonators has passed
two signals at "danger," one of which is a "stop"
signal.
Leaving the question of calling out the men, which
is inseparable from the system, and which, as will be
seen, leaves something to be desired, we may consider
the question of who, amongst those more immediately
concerned, is the most suitable person to say when the
ordinary visual signals shall be superseded by others
more adapted to the circumstances obtaining at the
time. Drivers and signalmen are equally interested
in the exhibition of suitable signals, but the former
differs from the latter, in that it is for his guidance
that the signals are exhibited, and that it is he alone
who controls that by which mischief may be wrought
in consequence of a misinterpretation of, or failure
to see, the signals exhibited. Hence it would appear
that the driver is the most suitable person to say
when he requires additional means to enable him to
obey the signals shown ; and considerations such
as those just adduced are alone sufficient to stamp
as inadequate any system of signalling, under excep-
tional circumstances, that cannot vbe brought into
operation at any time the person requiring it may
consider necessary.
120 RAILWAY SIGNALLING.
It might be thought that the absence of any signal:
at a point where a signal is usually displayed should,
of itself, be taken as a " danger" signal. This is the
usual practice, but it should not be forgotten that,
when running at a high rate of speed, the signals
passed are, during clear weather, one of the means
by which drivers of such trains localise their position.
If these and other landmarks, by which their position
might be noted, are obliterated, the difficulty of deter-
mining the precise spot at which a signal may be
expected becomes enormous. Another point in con-
junction with this localisation of position is that the.
method of fog signalling by detonators is partly
negative — i.e., the " all right " signal is given by the
absence of an explosion, and the exhibition of certain
visual signals by flag or hand lamp, which the driver
may or may not see. The localisation of their position
at any time is a matter of very great importance ta
drivers of fast trains, especially during unfavourable
weather, the more particularly as the time-table takes
no notice of fogs.
It is not necessary to pursue the subject further at
this point. Consideration will show that however
suitable the present system of fog signalling may
have been in times when traffic was smaller, and
trains ran at less speed, and carried considerably less
passengers than at present, the arrangements it
permits of being made are not in keeping with the
importance of the subject.
Attempts have been made at various times to place
the fog-signalling apparatus entirely in the hands of
the signalman by providing him with special apparatus
RAILWAY SIGNALLING. . I2T
by means of which he is able to place detonators in
position for explosion as occasion may require. The
usual means of doing this is a lever, similar to those
used for actuating the points and signals, communi-
cating by a wire with mechanism by which detonators
may be withdrawn one at a time from a watertight
box, in which they are placed, at a point near the
signal to be repeated. The rules for the working of
one form of such apparatus are given below :
INSTRUCTIONS FOR WORKING THE AUTOMATIC FOG-SIGNAL
APPARATUS.
1. A recorder in connection with the apparatus is fixed in the signal
cabin in order that the signalman may at all times know how many
unexploded detonators there are in the tube.
2. The ganger of platelayers is responsible for keeping the apparatus
charged with detonators, and he must always inform the signalman the
number of detonators placed in the tube, so that the signalman may set
the record to the correct number. When the signalman finds the stock
diminishing he must warn the ganger. A gong is attached, which sounds
as an indication that the tube is empty.
3. Before commencing fog signalling, if the apparatus has not been used
for some time, it will (or may) be found necessary, for the purpose of
adjusting the wire, to pull the lever over two or three times ; the distant
signal must be off while this is being done.
4. To commence fog signalling the fog-signal lever must be pulled over
and replaced in its normal position ; by these movements a detonator is
placed under the hammer ready for explosion, and will remain so while
the lever stands in its normal position.
5. If on the approach of a train the line is clear, the home, distant, and
fog-signal levers must be pulled over in the order named. By this move-
ment the detonator is removed ; to replace it the fog-signal lever must be
returned to its normal position, followed by the distant and home signal
levers.
6. When a detonator is exploded, the fog-signal lever must be pulled
over and returned (as directed in paragraph 4) ; this movement removes
the exploded signal and places another detonator under the hammer.
7. When the apparatus is not required for use, the fog-signal lever must
remain in the normal position.
122 RAILWAY SIGNALLING.
The number of such appliances in actual use is only
a small proportion of the number of places where
they might be used, and it cannot be denied that in
some cases they have done good work. The con-
struction of the mechanism, however, is such as to
place only one detonator in position for explosion.
A reference to the rules for ordinary fog signalling
will show that two detonators are always put in
position by the fog signalman. This, of course, is
to prevent misapprehension arising from the report
of one being weak or from one missing explosion, as
will occasionally occur.
The third instruction relating to adjustment pre-
vious to commencing fog signalling after a period
of disuse, indicates a disadvantage which arises from
the variation of the length of the wire with differences
•of temperature. Where the detonator must be placed
in an exact position for explosion, the possibility of
doing this without chance of error becomes less as
the distance increases.
Consideration of the rules for working this apparatus
shows that there is nothing of an automatic charcter
about it, although it is so designated.
Interlocking: of Points and Signals. — Although
forming no part of the signals exhibited, the inter-
locking of points and signal levers plays so important
a part in the safe working of railways as to make a
reference to it, however slight, indispensable. The
assemblage of the means of actuation of a large
number of signals and points in one cabin, and under
the control of one man or more, offers numerous
opportunities for mistake unless the levers of the
RAILWAY SIGNALLING. 123
various points and signals are so arranged as to
prevent the road being set for trains converging to a
common fouling point.
It is difficult to give more than a general idea of the
principles of interlocking, as each important centre
differs from others in its requirements. There are,
however, certain broad principles connected with the
order of interlocking that are followed in all cases,
which may be indicated thus :
The interlocking of a frame must be such as to
prevent the signals for any line being lowered to
" all right " until the points have been made right for
that road. In the case of ground discs the movements
are simultaneous.
The interlocking of a frame must be such as to
prevent a " distant " signal from being lowered to the
" all right " position whilst the " home " signal is at
" danger," and in some cases whilst the " advance "
is in that position also.
Where cross-over roads are used, the interlocking
must prevent the points being set for the cross-over
roads whilst any of the signals for either of the lines
are showing all-right signals.
At junctions the interlocking must prevent the
signals being set for one line whilst the signals for
another line are in such a position as would lead a
.train approaching on that line to a fouling point.
The points interlocking must be such that when the
points for one line are set, no train or engine which
may pass signals at " danger " can foul the train for
which the line has been set.
Siding points and signals leading to main lines must
124 RAILWAY SIGNALLING.
be incapable of operation when other signals are off
for trains on the main line.
The converse of all these requirements holds good,
of course. Generally, it may be said that the inter-
locking of the signals and points' levers is one of the
many devices adopted for controlling the controller,
and its importance to the general working of railways
cannot possibly be over-estimated.
EXAMPLES OF RULES AND REGULATIONS RELATING TO
FIXED, HAND, AND DETONATING SIGNALS AS USED
IN RAILWAY SIGNALLING.
HAND SIGNALS.
1. These signals will be made by hand or with flags by day, and
with lamps by night or in foggy weather.
2. In the absence of flags. — Both arms raised above the head denotes
" danger."
3. One arm raised above the head denotes "caution."
4. One arm held in a horizontal position across the line of rails
denotes "all right."
5. In the absence of a red light, any light waved violently denotes
" danger" — stop.
6. In shunting operations by night, a white light waved slowly up
and down means "move forward" — i.e., go away from the person giving
the signal ; a white light moved slowly from side to side across the body
means "move back" — i <?., come towards the person giving the signal
A green light used instead of a white light as above means "move
forward slowly" or "move back slowly."
A red light in all cases, or any other light waved violently, means
" stop."
7. Hand lamps and hand flags when used as signals, except where
they are employed for the purpose of marking the actual point of obstruc-
tion, must always be held in the hand, and not placed upon or stuck into
the ground.
FIXED SIGNALS.
I. Fixed signals consist of home signals, distant signals, starting
signals, and siding signals, and also of calling-on signals, which have been
adopted by some companies.
RAILWAY SIGNALLING.
125
2. On the majority of lines semaphore signals are adopted, but other
forms of signals are used by some companies.
3. The semaphore signals are constructed with arms for day signals
and lamps for night.
4. The signal is invariably made by the arm on the left-hand side
of the post as seen by the driver of an approaching engine.
SEMAPHORE DANGER SIGNAL.
SEMAPHORE ALL-RIGHT SIGNAL.
B.
SEMAPHORE CAUTION SIGNAL.
A. — ORDINARY SEMAPHORE.
B. — CALLING-ON ARM.
5. The semaphore " danger " signal is shown in the daytime by
the arm on the left-hand side of the post being raised to the horizontal
position (as shown above), and by the exhibition of a RED light at night.
6. The semaphore "all-right" signal is shown in the daytime by the
arm on the left-hand side being lowered to the post (as shown above), and
by the exhibition of a WHITE light by night.
7. On those lines where the semaphore "caution" signal is in use,
126 RAILWAY SIGNALLING.
it is shown on a fixed post in the daytime by the arm on the left-hand
side of the post being placed half-way to the horizontal position, and
by the exhibition of a GREEN light by night.
8. On lines worked on the block telegraph system two signals
only are exhibited at the semaphore — viz., " danger" and " all right," the
red light being in all cases the "danger" signal and the white light
generally the "all-right" signal; but some companies use the green
light as the "all-right" signal in all cases, and others (who use the red
and white light signals) use a red and a green light in the case of
junction signals in order to mark the position of the junctions.
9. On .... short " calling-on " arms are fixed upon some of
the home signal posts, as shown above, for the purpose of avoiding
hand signalling. When a " calling-on " arm is lowered, the engine driver
must draw forward past the post of the signal on which the " calling-on "
arm is fixed as far as the line is clear. If the signalman is ahead of
the "calling-on" arm, and the signalman in the box wants to communi-
cate with the driver, he must show a hand danger signal from the box
to stop him. The lowering of the "calling-on" arm is not, in any case,
an authority for the starting signal to be passed at danger.
10. Home signals are placed at stations, junctions, sidings, and
signal boxes, and when at danger no train or engine must pass them or
foul the crossings or points to which they apply, except as prescribed
in 13 and 23, or where "calling-on" arms are in use.
Home signals at junctions are, as a rule, so placed as to indicate
by their positions the lines to which they apply, and when more than
one are fixed to the same side of a post they apply generally as
follow — viz. :
The first or top arm to the line on the left.
The second arm to the line next in order from the left, and
so on.
11. Home signals at junctions must never be passed at danger,
except where "calling-on" arms are in use.
When a train has stopped at a junction home signal, and it is
necessary to bring it within the home signal before the section ahead is
clear, the signalman may, where a starting signal is provided, and that
signal is at danger, lower the home signal for the train to draw ahead.
The engine driver of any train which has thus been stopped at a
junction home signal must, after that signal has been lowered, go
slowly forward towards the starting signal, but must not pass the
starting signal until it is lowered.
12. Home signals at stations, sidings, and signal boxes (other
RAILWAY SIGNALLING. 127
than at junctions) where there are starting signals must never be
passed when at danger, except as stated in 23 or where ' ! calling-on "
arms are in use.
When a train has been stopped or brought nearly to a stand at
the home signal of a station, siding, or signal box (other than at
junctions) where starting signals are provided, and it is necessary to
bring it within the home signal before the block section ahead is clear,
the signalman may, if the starting signal is at danger, lower the home
signal for the train to draw ahead.
13. Home signals at stations, sidings, and signal boxes (other than
at junctions) where starting signals are not provided must never be
passed when at danger, except as follows, or where there are "calling
on " arms.
When a train has been stopped, or brought nearly to a stand at
the home signal, and it is necessary to draw it within such signal before
the line ahead is clear, the engine driver must, on receiving verbal
instructions from the signalman, draw past the home signal, so as to
bring his train under its protection ; if the signalman is too far from
the engine driver to be able to communicate verbally with him, the
engine driver must, upon the receipt of the necessary signal by hand
lamp or flag from the signalman, pass the home signal, and draw
cautiously towards the signal box as far as the line is clear, and there
await the verbal instructions of the signalman. The hand signals for
this purpose must be given only by a green light or a green flag.
Engine drivers must not go forward until they clearly understand
the verbal communication which the signalman has made to them as to
the state of the line ahead, and then only with their engines under the
needful control to ensure safety.
14. Signalmen must not lower the home signal for an approaching
train which has to stop at the starting signal until the train is close to
the home signal, and has been brought quite, or nearly, to a stand at
it. In foggy weather, or during falling snow, the engine driver must,
when practicable, be verbally informed that he is only to draw forward
to the starting signal.
The engine driver of any train which has been thus stopped, or
brought nearly to a stand at a home signal, must, after the signal has
been lowered, go slowly forward towards the starting signal, but must
only proceed so far as is necessary to leave the last vehicle well clear
of the points and crossings, and within sight of the signalman. The
starting signal must not be passed until it is lowered, except as
provided in 21.
128 RAILWAY SIGNALLING.
In case of detention at a home or starting signal the engine driver
must sound his whistle, and if still detained, the guard or fireman must
go to the signal box and remind the signalman of the position of the
train or engine, and remain there until the signalman can give permission
to go forward. In foggy weather, or during falling snow, the guard or
fireman must, immediately upon the train or engine coming to a stand,
proceed to the signal box.
When a train or engine has drawn past a home signal and is waiting
to be crossed to another line, or to be let into a siding, or has been
shunted on to the opposite running line, or has been placed on either a
main or branch line at a junction for another train or engine to pass,
the guard or fireman must, in all cases, when the train or engine comes
to a stand, proceed immediately to the signal box and remind the signal-
man of the position of the train or engine, and remain there until the
signalman can give permission to proceed.
The duty of going to the signalman must be performed under the
following instructions :
(a) In the case of a light engine, or of a passenger train with only
one guard, by the fireman ; the guard in the latter case remaining in
•charge of the train.
(b) In the case of a goods train with only one guard :
(1) When stopped at a home signal, by the fireman.
(2) When stopped at a starting signal, or at an advanced starting
signal, by the guard.
(3) When waiting to be crossed on to another line, or to be let into
a siding, by the guard.
(4) When crossed to the opposite side, by the fireman.
(5) When drawn ahead on to a main or branch line at a junction, by
the guard.
(6) When backed on to a main or branch line at a junction, by the
fireman.
(c) In the case of a train with two or more guards, by the guard
whose van is nearest the signal box ; if there is only one -van on the
train, by the underguard or brakesman.
The guard in charge of the train must satisfy himself that the man
whose duty it is to do so has gone to the signal box.
(d) In the case of a train or vehicles in charge only of a shunter,
the shunter must go to the signal box.
Sufficient time must be allowed for the guard, shunter, or fireman
ito rejoin his van or engine before the home or starting signal is lowered.
The man who goes to the signal box as a reminder to the signalman
RAILWAY SIGNALLING.
129
must satisfy himself by personal enquiry that the signalman is aware 01
the obstruction, and has protected the train or engine.
Where mechanical or other appliances are supplied to . serve as a
reminder to the signalman that certain signals must not be lowered or
turned off, he must make prompt use of such appliances ; and, in addition,
where the company's regulations require it, must " block-back " to the
signal box or boxes affected by the obstruction before allowing the line
to be obstructed.
When a home signal has been lowered for the passing of a train,
it must not (except in case of accident or obstruction) be again placed
at danger until the last vehicle of the train has passed it or the train
has been brought to a stand, nor, in the case of a junction, until the
last vehicle of the train has passed it and is clear of the junction points.
15. Distant signals are fixed at a considerable distance from the
point at which the home signal is placed. They are constructed to
exhibit the danger and all-right signals only, except in some cases where
they are constructed to exhibit the danger and caution signals only.
1 6. Where the semaphores are used as distant signals, the arms
are constructed thus :
SEMAPHORE DISTANT SIGNAL.
17. Where it is found necessary to place the distant signal arm
from a signal box in advance on the home or starting signal post of
the box in the rear, applicable to the same line, the distant signal will
be the lower and the home or starting signal the upper arm of that post.
1 8. Distant signals must be placed at danger immediately they are
passed by a train or engine, and must not, where block working is in
operation, be again taken off, except as prescribed by the block telegraph
regulations. They must also be placed at danger whenever any obstruc-
130 RAILWAY SIGNALLING.
tion or clanger exists upon the line they are intended to protect, and so
remain until the obstruction or danger is removed.
19. Whenever the distant signal is at clanger, the danger signal
must also be exhibited at the home signal, except when a train has
passed the distant signal at danger, or in the case of an approaching
train, for which both signals have to be taken off. In the latter case
the home signal must be taken off first, and the distant signal placed
at danger as soon as the train has passed it ; and in the former case
the home signal only must be lowered to allow the train to pass.
20. When an engine driver finds a distant signal at danger, he
must immediately reduce the speed of his train, so as to be able, in case
of need, to stop at such signal; but if he sees that the way in front of
him is clear, he must proceed slowly and cautiously within the distant
signal, having such control of his train as to be able to stop it short
of any obstruction that may exist between such signal and the home
signal, and must bring his train to a stand as near the home signal as-
circumstances will allow.
STARTING AND ADVANCED STARTING SIGNALS.
21. Where these signals are used, they are intended to control the
departure of trains into the section ahead, and must never be passed
when at danger, except as follows — viz.: Where the points of sidings or
cross-over roads are so near to a starting signal or advanced starting
signal as to render it necessary for the signal to be passed for shunting
purposes, engine drivers may, for the purpose of shunting operations,
pass the starting signal when at danger upon being directed to do so
by the signalman, either verbally or by hand signal, which must in all
cases be given by a green hand lamp or a green flag, but they must
not, under any circumstances, proceed on their journey until the starting
signal or advanced starting signal has been lowered, indicating that the
section ahead is clear.
22. When the line is clear between the starting and advanced
starting signals, the signalman may, when necessary, after a train has
been brought to a stand, lower the starting signal to allow such train
to proceed towards the advanced starting signal.
If the advanced starting signal be not lowered for him to proceed,
the engine driver must, after arriving at it, sound his whistle at short
intervals, and, if still detained, the rear guard, or the fireman in the
case of a light engine, must proceed to the signal box and remind the
signalman of the position of the train or engine, and remain there until
the signalman can give permission to go forward. Sufficient time must
RAILWAY SIGNALLING. 13!
be allowed for the guard or fireman to rejoin his van or engine before
the starting signal is lowered.
In foggy weather, or during falling snow, no train must be drawn
forward past the starting signal towards the advanced starting signal
except for station duties and shunting purposes. Advanced starting
signals must not be used in foggy weather or during falling snow for a
train to draw up to or stand at waiting "line clear."
23. Home, distant, and starting signals apply only to trains or
engines running in the proper direction on the main lines, and must not
be used for any other purpose. Trains or engines running in the wrong
direction on either line must be signalled by hand lamp or flag.
Trains or engines shunting from one main line to the other, or shunting
into or out of sidings connected with the main line, must, unless fixed
signals are provided for the purpose of signalling such operations, be
signalled either verbally or by hand lamp or flag as occasion may require,
it being necessary in such cases that the "danger" signal should be exhibited
at the home signal as well as at the distant signal for the protection o
the train or engine so employed.
24. When the exit from sidings is controlled by ground disc or
dwarf semaphore signals, no train or engine must leave the siding unless
the signal is turned off or lowered.
DEFECTIVE SIGNALS.
25. Every stationmaster, signalman, gateman, or other person must,
in the event of any home, distant, or starting signal under his charge
becoming defective, strictly carry out Regulations 34 and 35, and a
competent man, or, if necessary, two or more competent men, must be
selected, provided with the necessary hand signals and detonators, and
appointed to signal in place of such defective signal until it is again in
proper working order.
Where the circumstances of the case admit of such an arrangement,
the stationmaster must select proper men from his own staff for the
purpose ; but where this cannot be done, he must apply to the nearest
ganger for competent platelayers.
26. The absence of a signal at a place where a signal is ordinarily
shown, or a signal imperfectly exhibited, must be considered a danger
signal, and treated accordingly, and the fact reported to the signalman
or stationmaster.
DETONATING SIGNALS.
27. Every guard, signalman, engine driver, gateman, and ganger
of platelayers will be provided with detonators, which he is always to
132 RAILWAY SIGNALLING.
have ready for use whilst on duty ; and every person in charge of a
station must keep a supply of these signals in a suitable place known by
and easy of access at all times to every person connected with the station.
All persons above named will be held responsible for keeping up the
proper supply of detonators.
28. Detonating signals are to be used for the purpose of attracting
the attention of engine drivers. They must be placed on the rail (label
upwards), and the clasp bent round the upper flange of the rail to
prevent their falling off, and must be observed by engine drivers as
follows :
When an engine explodes a detonator in clear weather, the engine
driver must immediately shut off steam, reduce the speed, and bring his
train under such complete control as to enable him to stop at once if
required, and then proceed cautiously to the place of obstruction or until
he receives a further signal for his guidance.
When an engine explodes a detonator in foggy weather or during
falling snow, the engine driver must immediately shut off steam and bring
his train under complete control, so as to be prepared to obey any
signal that may be exhibited. If he receives a red or danger hand signal,
unless he be satisfied that the signal is exhibited for the purpose of
repeating a distant signal at danger, he must at once bring his engine to
a stand, and then proceed cautiously to the point the hand signal is
intended to protect, or until he receives a signal to proceed ; and if he
receive a green or caution hand signal, he must act in accordance with
36. If the red or danger hand signal be exhibited to repeat a distant
signal at danger, the engine driver may, after having shut off steam,
proceed cautiously in the direction of the home signal.
The absence of any signal after the explosion of a detonator must
be considered equal to the exhibition of a danger signal.
When used to repeat fixed signals and call attention to the fact of
their being at danger, the detonators must be observed in the same way
that such fixed signals would be observed if clearly seen to be at danger.
SIGNALLING IN FOGGY WEATHER OR DURING FALLING SNOW.
29. In the event of a fog or snowstorm occurring during the day
between 6 a.m. and 8 p.m., the men appointed to act as fog-signalmen
must at once report themselves to the stationmaster and take his
instructions ; those who have to do duty at junctions or intermediate
signal boxes away from a station must report themselves to the signal-
men on duty at the respective boxes.
30. When it is necessary to employ tog-signalmen during the
RAILWAY SIGNALLING. 133
night between 8 p.m. and 6 a.m., the stationmaster must arrange to
have the men called and sent to their respective posts. If the fog-
signalmen become aware from their own observation, or from infor
mation given to them, that their services are required during the night,
or at any other time when off duty, they must at once report themselves
to the stationmaster, or to the signalman at any junction or intermediate
signal box away from a station, without waiting to be called ; but this
will not relieve the stationmaster from the responsibility of sending for
the fog-signalmen when necessary.
When the fog has sufficiently cleared away or the snowstorm
ceased, the fog-signalmen must go to the signalman at the box in
connection with which they are employed, and take his instructions as
to whether their services are any longer required for fog-signalling duties.
31. A list of the names and addresses of the fog-signalmen, showing
the post to which each man is appointed, must be kept exhibited
in a conspicuous position in the stationmaster's office, signalman's box,
or other convenient place.
32. Each fog-signalman must, before proceeding to his post, be
supplied with detonators (not less than twenty-four), a hand signal lamp,
trimmed and lighted, and a red and a green flag. If signalling for a
distant signal, he must place himself outside the signal in connection
with which he works, and as far from it as is consistent with his
keeping it well in sight ; and whenever a train or engine has passed
him in the direction of the signal box from which the signal is worked,
and so long as the signal exhibits the danger signal, he must place and
keep two detonators fixed, ten yards apart, on one rail of the line for
which he is signalling, and exhibit a red hand lamp signal to the
engine driver and guard of an approaching train or engine, and when
the signal is lowered or taken off, he must remove the detonators from the
rail, and exhibit to the engine driver and guard an all-right hand signal
(in accordance with i, " Hand Signals,") by day, and an all-right signal by
hand lamp at night. If he become aware of any obstruction existing
on the line in the immediate neighbourhood of the signal for which he
is signalling, either from a train or engine not having gone forward, Or
from any other cause, he must leave the detonators on the rail and go
back along the line, showing a red light with his hand lamp, a sufficient
distance to protect such obstruction, and must there place on one rail of
the line for which he is signalling two detonators, ten yards apart, and
return to within sight of the distant signal ; and when he is satisfied
that the obstruction has been removed, he must take up the more
distant detonators, and then return to his post.
134 RAILWAY SIGNALLING.
When fog-signalmen are employed in connection with home or
starting signals, they must place two detonators, ten yards apart, on one
rail of each line for which the signal is at danger, and carry out any
instructions they may receive from the signalman on duty.
Men employed for fog-signalling, after having fixed the detonators
on the rails, must, when practicable, place themselves about thirty yards
within them — that is, nearer the fixed signal or obstruction for which
they are signalling — and so exhibit the hand signals that they may be
seen by drivers after the engine has exploded the detonators.
In repeating fixed signals when at danger, a red hand signal must,
in all cases, be used.
When a fog-signalman is unable to see the signal for which he is fog-
signalling, he must assume that it is at danger.
33. At all signal boxes (whether intermediate or otherwise) where
no fog-signalmen are appointed to repeat fixed signals, or where such
men are appointed but have not arrived, the signalman must, when he
requires to stop an approaching train, in addition to keeping his signals
at danger, place opposite his signal box, when it is practicable to do so,
two detonators on each line to which the danger signal is intended to
apply, sufficiently apart to give two distinct and separate reports.
REPAIRS TO SIGNALS, POINTS, INTERLOCKING FRAMES, LOCK BOLTS,
BARS, OR FACING POINTS.
34. The signalman must frequently examine and try his fixed signals
to see that they work well, are kept clean, and show properly. Great
care must be used in putting on a distant signal : it is not sufficient
merely to move the lever, but the signalman must at the same time
watch the signal or its repeater, so as to ascertain that it obeys the
lever and goes fully on to danger. He must take care that the signal
wires are kept at the proper length by means of the regulating screws
or links, so as to compensate for the expansion and contraction caused
by variations of temperature.
In the event of a home or starting signal becoming defective or not
working efficiently, a competent person must be placed outside such
signal with hand signals and detonators, and act under the instructions
of the signalman.
In the event of a distant signal becoming defective or not working
efficiently, a competent person must be stationed just outside the distant
signal with hand signals and detonators, and act under the instructions
of the signalman ; and when such person is out of sight of the home
signal one man or more must be stationed between that and the defective
RAILWAY SIGNALLING. 135
signal for the purpose of repeating, by hand signals, to the man stationed
at the distant signal the signals exhibited at the home signal.
35. When the interlocking of any lever frame, or any facing point,
bolt, or bar is out of order, or when any point or signal lever, or any
home, starting, or advanced starting signal, or siding signal applicable to
a siding not protected by safety points, is defective and not working
properly, one competent man or more, as may be necessary, provided
with hand signals and detonators, must be appointed to act under the
instructions of the signalman in charge of the signal box ; and the distant
signals applicable to the lines affected must be kept at danger by being
•disconnected from the levers by which they are worked, and must remain
in that position until the defect has been made good, and all is again in
working order.
When the interlocking of any signal box, or any facing point, bolt, or bar
is being altered or repaired, the fitter in charge of the work must give to
the signalman in charge of such signal box, an exact statement of the
signals and points which it will be necessary to work temporarily without
the safeguard of the interlocking, or the facing point, bolt, or bar.
The hand signalman appointed to signal in place of a defective
signal, or in consequence of the interlocking of a lever frame, or a facing
point, bolt, or bar being out of order, must ascertain from the signal-
man in charge of the signal box what train he is to bring forward, and
when such train has to run over points other than facing points he must
satisfy himself by personal observation that the points are in the proper
position for the train to pass. If the train which is to be brought
forward is approaching facing points, the hand signalman must, before
signalling it forward, inform the signalman in charge of the signal box
the position of such points, and satisfy himself that they are open for
the line on which the signalman in the signal box intends the train
should run.
The hand signalman must, when signalling a train forward, stand
near to the signal in place of which he is acting, in order that his
signal may not be mistaken by an engine driver on any other line, and
all trains must run past the place where the defect exists at a slow rate
of speed, the engine drivers being cautioned.
The signalman in charge of the signal box must take care that the
hand signalman is properly instructed as to his duties, and understands
what he has to do.
When any fixed signal is out of order, or is disconnected for purposes
of repair or otherwise, and the interlocking of the point and signal
levers is all right, the signalman must, to enable him to obtain the
136 RAILWAY SIGNALLING.
security of the interlocking, use the lever applicable to such signal as if
the signal was in work, and the signal and counter-balance weight
must, when necessary, be disconnected from the lever to admit of this
being done.
When the interlocking frame at a junction is out of order, the facing
points must, except when required to be otherwise placed for the
passage of trains, be so set that no engine or train can cross the path
of a train travelling in the opposite direction upon the adjoining line.
PLATELAYER'S CAUTION SIGNAL.
36. A green flag or a green light exhibited by platelayers indicates^
that trains and engines must reduce speed to fifteen miles an hour over
the portion of line protected by such green signal.
CHAPTER IV.
The first example of an electrical signalling instru-
ment in use with which the writer became acquainted
is that shown by Figs. 14 and 15. These instruments
were patented by Alex. Bain, and were in use between
the ends of a tunnel on the old Stockton and Dar-
lington Railway, and were replaced by C. V. Walker's
block instruments about 1868. The instruments were
provided with bells, not shown, the hammers of which
were held up by trip-gear, which was released on the
first deflection of the needle, the hammer being raised
again, by hand, after every stroke.
CODE OF SIGNALS AND ALPHABET.
Yes
Engine out
Two engines
Three engines
I understand
Engine entered
Stop traffic on by-way
No
I am going to speak
letters
Engine returned back
Is all right
Train on by-way
Sent train on by-way
A
I
IVI
B
II
IVII
C
III
IIVI
I)
IIII
VVI
E
V
IVV
F
vv
VIV
G
vw
WVI
II
vwv
IVVV
I
IV
VIVV
VVIV
j
IIV
WII
K
IIIV
VIVI
L
VI
M
VII
IVIV
N
VIII
O Is an engine near
P Send train on main-way
Q Stop traffic on main-way
R Repeat the last letter
S Do you understand
T Wagons left in
U Is all out
V No tail signal
W Hagger leases
X Train on main-way
Y All is right
Z I am showing the
graph to a friend
Stop traffic on by-way
tele.
RULES TO BE OBSERVED.— ist. The bell is to be rung at the commence-
ment of every conversation. — 2nd. The V in the course of conversation
always to form part of it and to be considered as the bell.— 3rd. At the
close of every conversation the bell handles must be set for ringing. — 4th.
The plates of the battery must be put into the trough at the beginning of
the conversation and taken out when finished.
138
RAILWAY SIGNALLING.
The code of signals in use for ordinary work and the
alphabet for conversation on matters not provided for
in the code are given, together with the rules. The
signal, " I am showing the telegraph to a friend," and
FlG. 14. — Alexander Bain's Signalling Instrument.
the rule, " The plates of the battery must be put into
the trough at the beginning of the conversation and
taken out when finished," are very quaint, and would
be difficult to duplicate at present. The signal,
RAILWAY SIGNALLING.
139
NEEDLE
TlG. 15. — Interior of Instrument, showing Commutator.
14° RAILWAY SIGNALLING.
" Engine returned back," is also significant of the free
and easy manner in which things were carried on in
the earlier days of railways.
Block Working. — " Block " working may, for con-
venience, be divided into two main parts, " absolute "
and "permissive." "Absolute" block may again be
divided into " double-line " and " single-line " working,
as the requirements for these are somewhat different.
Absolute block working consists essentially in pre-
serving a certain space between successive trains on
the same line of rails, this space varying in different
localities from a few miles to, perhaps, three hundred
or four hundred yards, or less, according to the amount
of traffic, the number of junctions, and the distance
between them.
Permissive block working imposes a space limit, not
between individual trains, but between groups of trains
only. With absolute block working, two trains in one
section on the same pair of lines are not permissible ;
with the permissive block, any number of trains up to
a prearranged limit may be admitted into a section.
The essential qualifications of block instruments for
ordinary double-line work are — reliability ; complete
independence of the indicating instruments for the
two lines of rails constituting the section ; distinctive
and easily understood signals ; continuous indication
of the condition of the line at all times, of such a
character that the indicating instruments will, in the
event of failure, synchronise with the conditions
under which the line or lines will be worked during
the existence of the fault ; simplicity of construction
and consequent freedom from derangement; capability
RAILWAY SIGNALLING. 14!
to deal with the code of signals without imposing a
great degree of intricacy ; freedom from chance of
error from outside influences, such as atmospheric
discharges, earth currents, or magnetic "storms,"
etc. ; flexible enough to allow of deviation, when
necessary, from the normal order of working ; and
last, but not least, the apparatus must be cheap and
easily worked.
Probably no forms of block instrument fulfil so many
of these requirements as the ordinary single-needle
instrument and bell block apparatus. For simplicity
of construction, flexibility, reliability, and distinctness
of signals it cannot be beaten. Being essentially a
three-wire apparatus, failure of one indicator affects
the line it represents alone, and the indications which
represent the active conditions of the line being
maintained by continuous currents, the indicators are
self-testing to a very large degree when in use for either
•" Line clear " or " Train on line." Failure of the
battery or line wire results in the indication " Line
blocked " being exhibited ; contact between a block
indicator line wire and another non-working earthed
wire results in the indication at one end, when an
active condition is being exhibited, being such as to
call attention to the fault and to afford an intimation
of its character ; whilst if the wire which is in contact
with the block wire is a working one, the effects are
quite different to the ordinary indications of the block
instrument, owing to the disturbing currents being
discontinuous and of irregular direction or duration.
Reversals due to lightning discharges, which at one
time constituted the most serious defect of the needle
142 RAILWAY SIGNALLING.
instrument, are now, by the use of induced needles,
unknown ; and the chief effect produced is, generally,
such as to render the instrument affected inoperative
by the short-circuiting of the lightning protector, or
when the effects are greater, owing to the " protector "
being part of the instrument it protects, by shattering
it from the explosive force developed by the discharge
at the sparking point.
The effects of earth currents, or disturbances of the
earth's magnetic field, are more marked, and from the
standpoint of the effects upon the block indicators are
of a more serious character, since they may cause
either of the active indications to be exhibited when
the condition of the line does not warrant either of
them being exhibited. Earth current effects may, as
already stated, be minimised by diminishing the
sensibility of the needles, and they are never of such
strength as to cause great deflection of the needle, or
such a deflection as is comparable with that due to
the working current. Disturbances of the earth's
field, however, produce much greater deviations at
times, but their occurrence is rare, and they are, more-
over, seldom of long duration, or perfectly steady.
The most striking instance of this class of phenomena
which has come under the author's observation
occurred about seven years ago, when the whole of
the needle circuits in a district extending over
thirty miles in length were affected for about three
hours. The instrument needles oscillated from side
to side, having a period of about three minutes,
during the whole time. That the disturbance was
due to magnetic variations, as distinguished from
RAILWAY SIGNALLING.
145
earth currents proper, or atmospheric inductive
effects, was shown by the continuance of the move-
ments of the needles of any circuit when the line
circuit was broken at any point.
This disturbance was not sufficiently strong to
interfere with the indications of the block instru-
ments under the influence of the working currentsr
but it caused considerable difficulty in ascertaining
the character of the signals sent, and completely
FIG. 16.
disorganised the telegraph service in the locality in
which it occurred. In general, however, such effects
are easily recognised by the signalmen, and it is always
possible to adjust the instruments so that the needle
when unaffected by the working current shall stand
on the centre line betwen " Line clear " and " Train
on line." This is effected by making the dial-plate
adjustable round the axis of the needle, as shown by
Fig. 16.
144
RAILWAY SIGNALLING.
The outer form of needle block indicator is generally
as shown by Fig. 9, which represents a sending or
non-pinning instrument. Fig. 17 is a diagrammatic
representation of the instrument showing the internal
UP LINE
FIG. 17. — Diagram of Single-Needle Instrument.
connections, which, as will be seen, are of the simplest
possible character. The commutator consists of a
horizontal barrel divided into two parts, which are
insulated from each other, and which by means of
flexible connections from the battery terminals, C Z,
RAILWAY SIGNALLING. 145
form the poles of the battery. The two vertical
springs, e and /, which are connected together by
the bridge piece, k, above the barrel, are the "line
springs," whilst the horizontal springs, g and h, are
the " battery springs." Movement of the instrument
handle in one direction, say to the right, causes C to
be brought into contact with e, breaking the latter's
connection with k at the same time, and Z in contact
with h. The current passes from
HOME STATION. DISTANT STATION.
C to <?, through lightning pro-
tector, P, instrument coils to A,
and line.
B to h, f, k, e, lightning protector
and instrument coils, to A and
earth.
B, k, and Z.
It will be noticed from the path of the current that
if one end of the line wire is connected to A at the
home station say, the other end must be connected
to B at the distant station in order that the deflections
of the needles may be similar, assuming that the
windings of the coils are the same in direction, which
is desirable for considerations connected with the
manufacture of the apparatus, and to make it inter-
changeable to the fullest possible extent. Reversal of
the instrument handle reverses the direction of the
current, and the deflection of the needle is reversed
in consequence.
The line springs, e and /, and the battery springs,
g and h, are the points at which mechanical failure in
this class of instrument is most frequent.
The continuous indications are maintained by the
10
146 RAILWAY SIGNALLING.
handle of the instrument being held over in the proper
direction by a peg inserted through the horizontal
portion outside the case, as shown by Fig. 42. In
some cases a trigger arrangement is substituted for
the peg. In both cases, however, the action is
mechanical, and dependent upon the proper use by the
signalman of the means provided. The pegging of
the needle in either of the active positions is done by
the signalman at the receiving end of the section as an
FIG. 1 8.— Diagram of Block Bell.
indication that he understands the signals previously
exchanged and acquiesces in what is being done by the
sending signalman, and also as a permanent indication
to both men of the state of things until the conditions
represented have been changed.
The bell used for exchanging code signals is the
usual single-stroke bell, and is shown diagrammatically
by Fig. 18.
The whole of the operations involved in signalling
RAILWAY SIGNALLING.- 147
the passage of a train through a section are very
simple, and the order of working being fully set forth
in the code and regulations given on pp. 49 to 70, it
is not necessary to refer to them further here.
The simplest case of block working is shown in
the diagram (Fig. 19), in which the cabin, A, is an
IT* \T e*.W*
FIG. 19.
intermediate point between two others of more
importance. Such a cabin is a mere passing place,
and is only of use for shortening what would, other-
wise, be too long a section for the amount of traffic
passing, and is, generally, to be found in connection
with some road crossing, or at a point near dis-
tributing sidings, or for stopping trains at a con-
D ifj D
TT TT ^-TT1
FIG. 20.
veniently situated point to a junction where two or
more lines converge. The next case in order of
importance is shown by Fig. 20, where a relief siding
is provided into which a train may be shunted in
order to allow more important trains to pass.
Fig. 21 shows a junction where three lines converge,
10*
148
RAILWAY SIGNALLING.
and Fig. 22 shows a particular case where the lines
connecting junction points form a triangle.
FIG. 21.
The diagrammatic representation of the wires and
instruments for such cases as Figs. 20 and 21 are
shown in Figs. 23 and 24 respectively for a three-
wire single-needle system.
RAILWAY SIGNALLING.
149
The case represented by Fig. 22 introduces the
;four hundred yards rule by which signalmen, in cases
Up Line Block,
Block Bell
•**
^ Up Line Block
Block BeTL
Dowry Line Block
Up Line
••xj
fl D-
Pinning Black Instrument
Q DiartanJb Signal JricKcattrry
JC Struck. £.£:
FIG. 23.
Telephone
Up Block
~ J~ UpBlcxb
BlockBdl
Block Bell
Dovm-Block
A ^ DownsBlock
^ *
e n n Downline
FIG. 24.
where the distance between successive cabins is four
hundred yards, or less, must, before accepting the
RAILWAY SIGNALLING.
" Is line clear " signal from the rear cabin, obtain;
its acceptance from the advance cabin.
The arrangement of apparatus for the case repre-
sented by Fig. 22 is given by Fig. 25, and is peculiar
for the means taken to obviate accidents likely to
arise from local conditions. In general, however, the
FIG. 25, — The words "Up Bell" in the centre of the diagram should!
be "Up Block."
difference between an ordinary section, and one under
the four hundred yards rule, is in the rule for the
acceptance of the " Is line clear " signal only, and
does not involve any difference in the apparatus.
In the case under consideration the " down " line
between E and D is on a falling gradient, and passes
RAILWAY SIGNALLING,
through a long tunnel between E and A. The block
cabins, A, B, C, and D, are each within four hundred
yards of the next, and the acceptance of an " Is line
clear " signal by A, for a train passing to D, is con-
ditional upon its acceptance by both C and D, the
latter being offered the " Is line clear" signal by C
before accepting it from A. Hence, before a train
can leave E for D, the line must be quite clear to the
latter point, or through three sections, and in order
that A may not accept a train from E without the
knowledge of C and D, the " down " line instrument
FIG. 26. — Subsidiary Block Indicator.
circuit between E and A is continued through indi-
cators fixed in C and D, which reproduce at those
places the indications of A's " down " line instrument
at any time. Hence there are two independent checks
on A's actions in accepting an " Is line clear'3 signal,
and the indications are also of considerable value to
C and D for the regulation of traffic to and from the
section C B.
The form of indicator connected in the continuation
of the " down " line wire between E and B, at C and
D, is shown by Fig. 26. The dials are divided and
OF THB
UNIVERSITY
152
RAILWAY SIGNALLING.
lettered in the same way as those of the block
instruments, but the signalmen at C and D have no
control over the indicators. They are merely used
to indicate the condition of the line between E and
B in order that the signalmen at C and D may not
undertake any operations involving the fouling of the
" down " line under such conditions as, by an error
I
i — — f
=c
^c
I — 1
>
I .
7=1
/ \
FIG. 27. — Switch (Plan).
Instruments in Circuit.
FIG. 28 —Switch (End View).
Instruments out of Circuit.
of judgment or failure of apparatus, would lead to
an accident.
Switching Block Apparatus. — It frequently
happens that a block cabin is not required to
be open during the whole twenty-four hours, owing
to the traffic being less than ordinary during part
of the time. Advantage is taken of this, wherever
possible, to economise labour by closing certain
RAILWAY SIGNALLING.
153
cabins at stated periods, and working the traffic
between the cabins on each side as a block section.
Thus, of three successive cabins, A, B, and C, B may
be closed from ten p.m. to six a.m., say, and the
section between these times would be from A to C.
The alteration in the lengths of the section would be
effected by a switch placed in B, which would be
turned to the appropriate position by the signalman
before leaving, and after giving notice to A and C by
the signals provided in the code for such purpose.
FIG. 29 AND 30. — Three- Wire Block Switch.
Or
Or
fc
DI
Ot
Qi
m
UJ
iO
Ifl
Jfl
Ifl
—i
_j
_,
Handle Vertical. Instruments
in Circuit.
Handle Horizontal. Instruments
out of Circuit.
The form of switch generally used for switching
three-wire circuits is shown by Figs. 27 and 28, and
the diagrams (Figs. 29 and 30) show the connections
in the switch for the two positions it can occupy.
The connections for a complete block cabin of the
simple character indicated by Fig. 19 are given,
diagrammatically, in Fig. 31, in which the switch
is shown with the connections arranged as when
154
RAILWAY SIGNALLING
RAILWAY SIGNALLING. 155
the cabin is closed. It will be noticed that the two
indicating instruments working to the " up " station
are in circuit, and will, therefore, reproduce all
signals sent from the cabins on either side. The
object of this arrangement is to enable the signalman
to ascertain, when opening out the cabin for ordinary
working, whether any trains are in the section he is
about to divide. If the block indicators show that
trains are in the section, or that the preliminary
signals for trains entering the section have been
acknowledged, the signalman at the cabin which is
being opened pins the instruments at that place
appropriately. If he gets the " Train passing out of
section " signal from the advance cabin, he also gives
that signal to the cabin in the rear, and afterwards
takes all succeeding signals himself. The code pro-
vides signals which indicate to the cabins on either
side when an intermediate cabin is being closed or
opened, so that the signalmen at the ends of the
long section know when they are working to each
other, and when to the intermediate cabin.
Another method of switching instruments in and
out of circuit, with a switch of similar construction, is
shown in diagrams Nos. 32, 33, and 34. In Fig. 32 all
instruments are earthed at that cabin which is open-
In Fig. 34 all instruments are cut out of circuit, and
the cabin is closed. In Fig. 33 the block indicators
are in circuit, but are working through between the
cabins on either side. With the switch in the latter
position the signalman is able to ascertain whether
there are any trains in the section he is about to
divide, in order that he may arrange to exhibit the
156
RAILWAY SIGNALLING.
RAILWAY SIGNALLING.
157
158 RAILWAY SIGNALLING.
proper indications on the block instruments at the two
cabins he will work to.
The essential difference between the two methods of
switching is that with the switch shown in Fig. 31,
one instrument for each line is constantly in circuit ;
with the switch shown by Figs. 32, 33, and 34, all
instruments are cut out of circuit until such time as
they are required to be brought into operation. It will
be noticed that with either form of switch no altera-
tion of battery power is made at the cabins which
are working through another which is closed. The
batteries are always installed with a margin sufficient
for the maximum distance they have to work through.
Walker's Block Instrument. — The external appear-
ance of this instrument is shown by Fig. 8. The
•connections for a block section are shown by Fig. 35,
and further details of the mechanism are given by
Fig. 36. Details of the construction of the signalling
key are given by Fig. 37. The upper electromagnets
work the white arm, and the lower work the red arm
and bell. The current passes through the upper coils
at the home station, and through the lower coils at
the distant station. The signalman at any station,
therefore, works the white arm at his own station,
and the red arm and bell at the distant station
simultaneously. The signalling key is simply a
current reverser. The upper, or white, knob sends a
current through the upper coils at the home station,
earth, lower coils at the distant station, line, to zinc
at the home station. The result is to raise the white
arm and red arm at the home and distant stations
respectively, and the bell at the latter place is also
RAILWAY SIGNALLING.
159
rung. The lower, or black, knob reverses the direc-
tion of the current and lowers the arms at the two
stations and also rings the bell at the distant station.
Both sets of electromagnets actuate polarised and
non-polarised armatures. The V-shaped permanent
UP STATION
DOWN STATION
UNC
FIG. 35.— Double- Line Block Circuit— Walker's Instruments.
magnets actuate the arms when a current passes in
the proper direction. The non-polarised armature,
a, of the upper electromagnet locks the polarised
armature in position. The non-polarised armature,
a', of the lower electromagnets carries the bell hammer,
and also locks the polarised armature in position.
i6o
RAILWAY SIGNALLING.
It will be noticed that descriptive signals must be
given by a bell code ; and, also, since the bell is rung
by the depression of either of the two knobs of the
signalling key, either would serve for sending train-
distinguishing signals by bell code if there were no
other considerations to take into account. The
particular knob to be used at any time, howeverr
FIG. 36.
depends entirely on the indications exhibited by the
instruments. Thus, suppose a train to be in the
section on the " down " line, and a train is to be
signalled on the " up " line. The signalman at the
sending end for the "up" line must give any bell
signals on the white knob, or he will lower the arms,
representing the condition of the "down" line. On
the other hand, the signalman at the receiving end for
RAILWAY SIGNALLING.
161
the " up " line must acknowledge bell signals on the
black knob, or he will raise the arms representing the
" up " line prematurely. If there are no trains in the
section, bell signals are given and acknowledged on
the black knob. The position of the arms is horizontal
when trains are in the section ; when no trains are
V
' • <! ©
< r."
—
3*
V
/
e
1
* ~*
le
' —
FIG. 37.— Walker's Double-Current Key.
passing the arms are lowered. There is, therefore,
no indication corresponding to "Line clear" or section
ready for train to enter with this form of instrument.
Preece's Block Instruments. — Another form of
block instrument for use with transient currents and
one line wire is shown by Fig. 38, which represents
ii
1 62
RAILWAY SIGNALLING.
diagrammatically the connections for a block circuit
using Preece's block instrument. In this form of
instrument the indicator for approaching trains is of a
different form to that for receding trains, in additiort
FIG. 38. — Double-Line Block Circuit — Preece's Instruments, One- Wire.
to being in a different position on the face of the
instrument. The " on " " off" disc at the upper part
of the instrument is the indicator for trains passing
from that station ; the semaphore arm is the indicator
for trains approaching that station. The disc indicator
RAILWAY SIGNALLING. 163
at the sending station is practically a repeater for the
semaphore arm at the distant station, in that its
movement shows that the actions of the signalman at
the distant station have been such as are calculated to
lower the semaphore arm at that place. The position
of the disc is " on " and the corresponding position
of the semaphore indicator is horizontal, both when
trains are actually passing through the section and when
it is clear of trains, but the difference between these
conditions is indicated, where a three-position switch
is used, by the switch handle being placed in the
position marked " Train on line." There are thus,
practically, three different indicators in this form of
instrument. Diagram Fig. 38 is drawn to show "Line
clear" for a train ready to proceed from the "up"
station to the " down " station. The handle of the
switch, S, occupies the "off" position shown at the
" up " station during the time the " Line clear "
signal is being exhibited only.
The construction of the instrument presents several
points of interest in the methods adopted to ensure
efficiency. The disc indicator is actuated by the
polarised armature of m1, and the bell is worked by
a non-polarised armature on the same electromagnet.
The position of the disc depends, therefore, on the
direction of the last current passed through m1, whilst
the bell is rung by all currents passing through that
electromagnet. The currents passed through ml are
from the local battery, and their direction depends
upon the position of the switch, S, at that place. The
semaphore arm is held in a horizontal position by the
detent, I, attached to the non-polarised armature of
II*
164 RAILWAY SIGNALLING.
m2, and also by the forked lever, g, which rests saddle-
wise on the bar connected with the polarised armature
of m3. There are thus two electromagnets to actuate
before the semaphore arm can be lowered, and these
must be acted upon in a prearranged order. In
addition to the polarised armature, n, mz actuates a
non-polarised armature, which completes two local
circuits each time a current passes through m3. One
local circuit is through w4, and serves to magnetise
the armature, n, and the cores, s, of m3, the direction
of magnetisation depending upon the position of the
switch. The electromagnet m2 is short-circuited when
the polarised armature of mB occupies the position
shown at the " up " station, and is not, therefore,
affected by currents when the switch is in the " on "
position. If the switch at the "up" station, say, is
put into the "off" position, and the plunger, k, is
depressed, a current will pass via earth m3 at "down"
station line, short-circuit of m* at the " up " station,
and the switch lever to zinc. The current operates
the two local circuits at the " down " station by the
non-polarised armature of tnz. One local circuit rings
the bell and the other magnetises the polarised
armature of w3, and causes the latter to take up the
position shown. The forked lever, g, is released, but
is still held in position, together with the semaphore
arm, by the detent, /. The movement of the polarised
armature of m3 to the position shown at the "down "
station breaks the short-circuit of m*. If the plunger,
k, at the " down " station is depressed in reply, a
current is sent via m2 at the " down " station, line,
and k, m3 at the " up " station, and earth to zinc at
RAILWAY SIGNALLING. 165
the " down " station, m3 at the " up " station closes
the local circuits and moves the disc indicator to the
"off" position. The instruments are then in the
position shown, which indicates "Line clear" for a
train to pass from the " up " to the " down " station.
When the " Train on line " signal is to be sent, the
switch at the sending end is put into the appropriate
position and the plunger depressed. The current
being in the opposite direction to that for "Line
clear,'' attracts the polarised armature of ms, and
through the forked lever, g, raises the semaphore arm,
where it is again caught by the detent, /. The reply
signal to the " Train on line " causes the disc
indicator to occupy the " on " position, since the
direction of the local current has been altered by
placing the switch to " on."
It will be noticed from the diagram that the
switches when in the " Train on line " position do
not affect the currents sent from the home station
in any way different from those produced when the
switches are in the " on " position, and the clearing
bell signals may be given and acknowledged with the
switches in either of these positions. The difference
between the "Line closed" and "Train on line"
indications are merely shown by the position of the
switch lever for the signalman's information. It will
be further observed that the obviously most important
signal of " Line clear " can only be exhibited by
concurrent action on the part of the signalmen at
the ends of the section, and unless the actions are
carried out in proper sequence no such signal will
be exhibited. The semaphore arm at the receiving
166
RAILWAY SIGNALLING.
end is lowered by the direct action of the signalman
there, but only after his instrument has been prepared,
so to speak, by the action of the signalman at the
sending end, and the same action notifies the sending
end of what has been done independently of the bell
signal. On the other hand, the semaphore arm is
FIG. 39.— Harper's Single Plunger Block.
raised by the direct action of the signalman at the
sending end when the " Train on line " signal is sent.
Harper's Block Instrument. — A further example
of the single-wire block instrument is shown by the
Diagram Fig. 139, which represents Harper's form
of instrument. There are in this instrument two
different forms of indicator; the lettered discs seen
RAILWAY SIGNALLING. 167
near the bottom of the instrument show what signal
has last been sent for one line, and the semaphore
arms indicate what signal has last been received for
the other line. The movement of the discs into their
proper position alters the direction of the current
through the electromagnets at both stations. These
currents are sent by the depression of the plunger
at the bottom of the instrument. When the disc
" All clear " is being shown, the plunger depresses
the long spring on the right hand, breaking contact
with a, making contact with d, and completing the
circuit between b and c by the insulated cross-piece, h.
The current passes by b c, and the lower electromagnet
at the home station to earth, the relay, the upper
electromagnets, alf left-hand spring, a, and right-hand
spring, at the distant station, line, right-hand long
spring, d, and zinc at the home station. When the
disc indicator is in the position shown, or indicating
" Train on line," the left-hand long spring is depressed
by the plunger, and the direction of the current is
reversed. Since the bell is rung by a local current,
the circuit of which is closed by a non-polarised relay,
it is obvious that the bell will be rung at the distant
station at every depression of the plunger at the home
station. Currents passing through these instruments
actuate the lower electromagnets at the home station
and the upper electromagnets at the distant station,
and, since the position of the disc indicator controls
the direction of the currents, it follows that the disc
indicator at the home station must be set to the
appropriate position before the signal can be given.
The positions of the semaphore arms are in accordance
168 RAILWAY SIGNALLING.
with the signals sent and received respectively for the
lower and upper semaphores, and by their position
represent the character of the indication exhibited by
the disc indicator at the distant station, in so far as
the difference between the " All clear " and the " Train,
on line "or " Train blocked " signals is concerned, but
do not indicate the difference between the two last-
named conditions of the line. Obviously, the differ-
ence between the " Line blocked " and " Train on
line " indications at any one station exercises no-
influence on the character of the indications at the
distant station.
Fletcher's Combined Block. — Fig. 40 is a diagram
showing the connections for a double-line block circuit
with Fletcher's block instrument. In this form the
bell-signalling apparatus is entirely distinct from the
indicating apparatus, and three line wires are required.
The indicators show "Line clear," "Train online,"
and " Line closed " by the different positions of one
indicator. The " Line clear " and " Train on line "
indications are maintained by continuous currents.
" Line closed " is indicated when no current is passing.
All currents pass through the lower electromagnet
at the home station and the upper electromagnet at
the distant station. If the commutator at the "down'*
station, say, is turned to the left, the springs, a and b,.
c and d, are connected, and a current passes to earth
at the home station, through the upper electromagnets
at the distant station, the line, the lower electro-
magnets, and the springs d and c, to zinc at the
home station. If the commutator is turned to the
right the direction of the current is reversed, the
RAILWAY SIGNALLING.
169
springs a and d being connected, and also the springs
b and c, and the character of the indication exhibited
is altered accordingly.
170
RAILWAY SIGNALLING.
Tyer's Semaphore Block Instrument. — The instru-
ment shown in diagram, by Fig. 41, is Tyer's
semaphore block. In this form of instrument the
signals are sent by the plunger, P, and the direction
of the currents is controlled by the position of the
commutator, C, which also carries the disc indicators
FIG. 41, — Double-Line Block Circuit— Tyer's Semaphore Block
Instruments.
" Line clear " and " Train on line." Currents pass
through the lower electromagnets at the home station,
and the upper electromagnets at the distant station.
The upper magnetising coils, M, are brought into use
by the relay : the lower magnetising coils, M1? are
traversed by the currents sent from the home station.
RAILWAY SIGNALLING. 17!
As shown in the diagram the instrument makes no
distinction between " Train on line " and " Line
closed," but in later instruments this distinction is
made.
Automatic Instruments. — The instruments already
described are all of a non-automatic character, and
depend entirely upon the action of the signalman for
the exhibition of the indications corresponding to the
various stages of signalling. As has already been
remarked, the signalman is not infallible, and a study
of the causes of accidents, which have from time to
time occurred, shows the necessity for more or less
control of the actions of the signalman.
One of the most important points at which attempts
have been made to control the action of the signalman
is the automatic locking of the block instruments in
the " Train on line " position, until the train so
signalled has passed a certain prearranged point in
the vicinity of the receiving end of the section, thus
preventing the signalman from accepting a second
train before the first is clear of the section.
Such action, resulting from a lapse of memory on
the part of the signalman at the receiving end of
the section, was found to be the cause of a very
bad accident a few years ago. An experimental
attempt to neutralise the effects likely to arise in
this way for a three-wire single-needle circuit is
shown by Figs. 42, 43, and 44.
As will be seen from the figures, the apparatus
provides for the locking of the instruments to " Train
on line," after the usual distinguishing signals have
passed, until the train so signalled has passed over
172
RAILWAY SIGNALLING.
a rail treadle, placed at a suitable point near the
cabin at the receiving end of the section. The
locking takes place at the receiving end of the
section, and is due to concurrent action on the part
of the signalmen at both ends.
The arrangement was not intended to relieve the
signalman of the responsibility for seeing that the
whole of a train, previously signalled, arrived and
passed under the protection of his outdoor signals
FIG. 42. — Case Removed, Instrument Locked (Right Elevation).
in accordance with the rules provided for working
traffic, but was designed with a view to provide a
check against any attempt he might, inadvertently,
make to clear the line before the train reached
a point which had previously been determined by
the responsible officials to be outside the section
referred to.
At the time the additional apparatus was designed,,
it was the rule for the signalman at the sending end
RAILWAY SIGNALLING.
173
to hold the instrument needles to "Train on line,"
until the signalman at the receiving end had inserted
the peg as shown in Fig. 42. At the instant this
was being done the batteries at both ends of the
section were in use. Advantage was taken of this
simultaneous use of both batteries to lock the handle
of the receiving instrument in the " Train on line "
position, so that if the peg was withdrawn before
the proper time the instruments at both ends would
FIG. 43. — Back Elevation, Instrument Locked.
still show " Train on line," and the signalman at
the receiving end would be unable to move the
handle to give " Line clear," or any other signal,
until the instrument was unlocked by the direct
action of the train signalled on its arrival at some
point where, at least a portion of the train, had passed
the signal cabin.
The additional apparatus consists of the differential
electromagnet, E1? which is connected as shown in
RAILWAY SIGNALLING.
Fig. 44, and the simple electromagnet, E, connected
with the rail treadle. The commutator spindle, d, is
prolonged through the back of the instrument, and
carries the slotted sector, s. The rocking-bar, a, rides
on the top of s when the handle of the instrument is
vertical ; and the armature of E! supports it, under
the lower edge, during the time the instrument is
being worked to send train-distinguishing signals,
since Ex is a differential electromagnet, and its-
UP STATION
FIG. 44. — Diagram of Connections.
armature is unaffected by currents originating at the
receiving end.
During the time train - distinguishing signals are
being received from the sending end of the section,
the armature of Ej is affected, but the handle of the
receiving instrument being then vertical, a is upheld
by s. If the handle of the instrument at the receiving
end is held over so that the needles indicate "Train
on line," the slot in s comes under the friction wheel
RAILWAY SIGNALLING. 175
of a, but the latter is still held up by the armature
of EX. If, now, the handle at the sending end is also
held over, the previous balance of the currents in
E! is upset, the armature is attracted and allows a to
fall and lock the handle of the receiving instrument
in the " Train on line " position. The only legitimate
means of releasing the handle after the operations
described is, as will be seen, by the current set up
when the circuit of E is closed by the depression of
the rail.
In Fig. 44 the handles of the instruments at both
ends of the section are shown in the position to
indicate " Train on line." It will, however, be clear
from the description that the diagram represents the
position of the handle at the sending station at the
moment the instrument at the receiving station is
being locked only. At other times the handle of the
sending instrument stands vertical, as usual, and the
" Train on line " indication is maintained by the
position of the handle at the receiving end. As has
already been said, this concurrent action of the two
signalmen was the rule for working at the time the
additional apparatus was designed. At present the
method of working is different, but there is nothing
in the requirements which is inimical to the working
of the instruments as indicators.
The position of the releasing treadle requires judg-
ment in its selection, and would probably, owing to
local circumstances, be different at every place. Its
position would also largely depend upon the rules in
use by the particular company adopting any such
method of automatic working. Some companies
176 RAILWAY SIGNALLING.
prohibit the acceptance of any train from the rear
when the previous train is standing at the " advance "
signal, although it is then protected by the " home "
signal. Others prohibit the acceptance of passenger
tiains only under these circumstances, and allow
goods or mineral trains to be brought to the " home "
signal, when a similar train is standing at the
" advance " signal, the " distant " being kept at
danger during the approach of the second train.
Obviously, the point of release will be different in
the two cases ; for if the line may not be cleared
until a train has passed the " advance " signal, the
releasing point must be situated so that it cannot be
actuated until the train has passed that signal, whilst,
•on the other hand, where the line is cleared when
the train is within the " home " signal, the releasing
point must be selected at a point near that signal.
This difference in practice is worthy of more notice.
In the case where the line is not cleared until the train
is passing the " advance " signal, the section obviously
extends between "advance" and "advance." Where
the line is cleared when the train is within the pro-
tection of the " home " signal, the section extends
between the " advance " at the sending end and the
" home " at the receiving end, and the part of the
line between the " home " and " advance " signals is
practically unblocked and worked under the observa-
tion of the signalman only.
Winter's Block Instrument. — Fig. 45 shows dia-
grammatically the construction of and connections
for Winter's block instrument as arranged for double-
line working, with one line wire and using transient
RAILWAY SIGNALLING.
177
currents. All distinguishing signals are given by a
bell code, and the indicators are simply used to show
the condition of the line for the time being.
12
178 RAILWAY SIGNALLING.
The apparatus provided at one station for one
section consists of a plunger key, P, a reversing
switch, S W, a small push, V, and the two indicator
dials. The indicating pointer for approaching trains
is coloured red, that for receding trains is black.
The soft-iron needles, e e, which are attached to the
same axle as the indicating pointers, behind the
dials, are polarised by the bar magnet, N S, and
play between the pole-pieces of M1 and M2. The
electromagnets, M1 and M2, are shown partly in front
view and partly in side view. M1 actuates the bell
hammer, and M2 actuates the polarised relay tongue,
T. The relay, R, is a combined polarised and non-
polarised electromagnet, and is also shown partly in
front view and partly in side view in order to show
the various actions more cleaiiy. All currents passing
through the coils of R cause the soft-iron armature, a,
to be attracted ; the tongue, t, is only attracted to the
stud, W1, when the current passes in the proper
direction. The switch, S W, is a commutator for
reversing the line battery. The carbon is attached
to the axle which carries the stud shown ; the zinc
is connected to the bridge, n. If the handle of the
switch is turned from " off," as shown, to " on," the
stud brings the carbon into connection with the
"on" line spring, and allows the "off" line spring
to make contact with the bridge, n, and zinc. The
plunger key, P, has three contact points between
I and /, between / and r, and between the plunger
and g. When the plunger is at rest / is in contact
with r, and the other contacts are broken. When;
the plunger is depressed, contact is made between*
RAILWAY SIGNALLING. 179
the plunger and g and between / and /, whilst the
connection between / and r is broken. The insulating
piece attached to / prevents contact between / and g
when the plunger is depressed. The push, V, when
depressed makes two contacts — one between d and k,
and the other between h and m. The two connectors
bridging d and k and h and m respectively when V
is depressed, are fastened together by an insulating
piece. The normal position of the switch, S W, is
" off," and it is only brought into use for approaching
trains. Signals originating at the station from which
a train is being dispatched are given with the switch
at " off." The normal position of the indicators is to
" Cleared line " when the section is not occupied.
When a train is ready to proceed from the " up "
station the operations to be gone through are as
follows, for block working only.
UP STATION. DOWN STATION.
Depresses P in accordance with
code for "Is line clear" signal.
Switch at "off." Receives "Is line clear" signa
on bell. Switch at "off." Puts
switch to "on" and depresses PI
in accordance with code for " Line
is clear " signal.
Receives "Line is clear" signal
on bell. Depresses P in accordance
with " Line is clear acknowledg-
ment " signal, and at the same time
depresses V. "Train going to"
indicator put to "On line." "Train coming from " indicator
put to "On line."
On the arrival of the train at the down station :
Puts switch to "off" and
depresses PI in accordance with
" arrival " signal.
12*
i8o
RAILWAY SIGNALLING.
Receives "arrival" signal on bell.
Depresses P in accordance with
"Arrival acknowledgment" signal,
and at the same time depresses V.
" Train going to " indicator put to
"Cleared line." "Train coming from " indicator
put to "Cleared line."
The paths of the various currents are as follows :
" Is line clear " signal.
From the line battery, C, through
the axle, S W, " off" line spring
/; / to the line L.
From earth, through ' ' on
spring and bridge, «, to Z,
line
From the line L, through r and
the coils of RI to earth.
a\ is attracted.
Local action, ringing bell (line
battery) :
From C through axle S Wi,
"off" line spring M3, "on" line
spring and bridge, n, to Z.
" Line is clear " signal.
Switch at " on." From C
through axle S Wi to earth.
From earth, through coils of R,
and r to line L. From line L, through /•[, /j, and
"off" line spring to Z.
/ is moved to Wi, but no current
is established owing to the break
in local circuit between d and k.
a is attracted, ringing bell.
Local action (line battery) :
From C through axle S W, " off"
line spring MI, "on" line spring
and bridge, «, to Z.
" Line is clear " acknowledgment.
Line battery.
From C through axle S W, " off"
line spring /, and / to line L. From line L, through r\ and
coils of RI to earth.
RAILWAY SIGNALLING. l8l
From earth, through " on " line
spring and bridge, n, to Z. a\ is attracted.
S Wj is to "on."
Local battery C M Z. From C, through axle S Wi,
From C, through K, d, Wl5 u, "on" line spring M3, "off" line
T, and outdoor semaphore to Z. spring and bridge, », to Z.
This puts " Train coming from "
indicator to " On line."
Local battery M Z.
From M, through ;;/, ^, P, g,
M3, K, T, and outdoor semaphore
loZ.
This puts " Train going to "
indicator to " On line."
Where the outdoor mechanical signal is interlocked
with the block instrument, a slight variation in the
order of the operations is made. This consists in
depressing V alone, at the sending end, after the
receipt of the " Line is clear " signal, and before the
" Line is clear acknowledgment " signal. This com-
pletes the circuit of C M Z alone, and unlocks the
mechanical signal. The subsequent depression of V,
together with P, for the " Line is clear acknowledg-
ment " signal moves the tongue, T, against %, and
prevents any current being sent to the outdoor signal
locking apparatus until after the " arrival " signal has
been received and acknowledged.
When the train, the signalling of which has been
traced in the route diagrams, arrives at the down
station, the switch, S W1? is put to " off," and the
plunger, P, is depressed in accordance with the
" arrival " signal. This signal simply rings the bell
at the up station, and puts t back to W. When
the " Arrival acknowledgment " signal is sent in reply
from the up station, the currents established by P
l82 RAILWAY SIGNALLING.
and V place the indicators at both stations to
" Cleared line," and the relay tongue, T, to u2.
The paths of the currents are easily traced when it
is remembered that the switch at the down station
has been put to "off." The local current at a^
(down station) is reversed, and puts the indicator at
that place to " Cleared line." The indicator at the
up station is placed to " Cleared line " by the action
of the battery, C M, the current passing through V.
The interlocking of the starting signal with the
block instrument is shown by Figs. 46, 47, and 48.
The crank of the lever, L (Fig. 46), is worked by the
signal lever in the cabin, but its operation differs from
that of most signal levers in that it is not required to
hold L up during the time the signal is " off." Fixed
to the axle of L, and working with it, is the cam
lever, c. Immediately above c, and in contact with it,
is the straight lever, /, with its counterweight, w. At
right angles to / is the counterweight, wlt carried
by a crank pivoted at p, the short arm, k,- of which
bears against / when the latter is horizontal. If the
lever L is raised, / is also raised by the cam, c, and k,
by the falling of wl9 is brought under /, and supports it
when the lever L has returned to the position shown
in Fig. 46. Fig. 47 is drawn to show the positions of
the various parts of the apparatus at this stage. So
far as the mechanical portion of the apparatus is
concerned, the signal arm is free to take up the "off"
position, but it is still held up by the electrical
interlocking apparatus, which is contained in the
box, B, at the top of the post.
The mechanism connected with the electrical inter-
RAILWAY SIGNAL
locking is shown separately in Fig. 48. It consists
of the simple electromagnet, R3, its armature, i, and
three cranks, one of which carries the hammer, /.
The axle of the signal arm is shown at a. The
WINTER & CRAIK'S
ELECTRICALLY INTERLOCKED SEMAPHORE
B
Nrrmil poSKioa cf Krut
FIG. 46.
Arm re tea se
FIG. 47-
tJ
l',A.'V^\_/v_A^J
FIG. 48.
lever, b, and the projection, m, work with a, and
under normal conditions b is locked by cr Before
the releasing current passes through R3 the lever, g,
is locked by the armature, but when the armature is
184 RAILWAY SIGNALLING.
attracted g is released, and / falls upon e and releases
6. If the operation of L, previously described, has
been performed before the releasing current passes,
or is performed after, the signal arm falls. The
projection, m, engages with n, when the axle, a, turns
and raises the hammer, /, and g, engaging with the
armature, i, locks / in the position it previously occu-
pied. When the train passes the signal, the depression
of F pulls k from under /, and the weight, w, being
free to fall, raises the arm to a horizontal position
again.
The apparatus is now fully in position for a similar
cycle of operations. The signalman, however, is not
able to again lower the signal arm until the " arrival "
signal has been received and acknowledged for the
last train signalled, owing to the tongue, t, of the
relay, R, being in contact with Wj (Fig. 45)) during
the time the " On line " indication is being exhibited.
It will be noticed from the description of the
apparatus and the method of working that the
principal objects aimed at in the design are concurrent
action on the part of the two signalmen concerned
before the section can be occupied or the signal
lowered for a train to pass forward, and automatic
protection of the section occupied by the raising of
the signal to danger by the passage of the train
over the rail treadle. The apparatus provides,
indirectly, by the position of the switch, an indication
similar to " Line clear " (section ready for train to-
enter) at the receiving end, but does not provide a
similar indication at the sending end.
Saxby-Farmer. — The special apparatus for ensuring
RAILWAY SIGNALLING. 185,
safety of working already described has been of a
partial character only, and adapted to meet given
circumstances. Figs. 49 - 61 illustrate Saxby and
Farmer's union of the locking apparatus of the
mechanical signals with the block signalling apparatus,
and constitutes a more complete attempt to meet all
the contingencies which can be foreseen. The objects
aimed at in the design, besides the ordinary block
signalling, are (a) the locking of the instrument handle
at the receiving end of the section, until the train
signalled has passed a prearranged point at that
place ; (6) the locking of all points and signal levers,
the operation of which involves fouling of the running
line, for all positions of the block instrument handles,
except the normal position, when the section is
unoccupied; (c) the locking of the "starting" or
" advance " signal to danger for all positions of the
block indicators except " Line clear " ; (d) ensuring
the raising of the signal to danger when it is no
longer required to be "off" for the train signalled,
and accepted, to proceed. The block indicator and
signalling apparatus follows the usual line of design for
single-wire instruments, and consists of a ringing and
signalling plunger, a commutator for reversing the
direction of the currents sent, the electromagnets for
working the semaphore indicators, a relay, and a bell.
All signals are given by the plunger, and the direction
of the currents so sent is controlled by the position
of the handle of the instrument. Currents pass^
through the electromagnets actuating the lower sema-
phore indicator at the home station, and through the
upper electromagnets at the distant station. The
i86
RAILWAY SIGNALLING.
non-polarised relay is actuated by all currents, and
the bell is rung accordingly. In connection with the
upper semaphore arm is a mercury contact switch,
which makes or breaks a circuit passing to the
starting signal according as the semaphore arm is
down or up. A similar switch is worked in connection
•with the mechanism provided for locking the handle
FIG. 49.
FIG. 50.
of the block instrument. This switch completes a
circuit through the handle-releasing coils and a rail
treadle which brings them into action, when the
handle is on the " Train on line " position, and
breaks the circuit when the handle occupies either
the " Line clear " or " normal " (line blocked)
positions. Besides these two switches there is an
RAILWAY SIGNALLING.
187
'electromagnetic two-way mercury contact switch, in a
separate case, which is used in connection with the
working of the starting signal.
Fig. 49 is a side view of the instrument with the
case removed, and shows the general arrangement
of the indicator electromagnets, A, handle-releasing
•coils, B, the ringing and signalling plunger, P, the
FIG. 51.
FIG. 52.
commutator, H, and the switch, S, in connection
with the upper semaphore arm. Fig. 50 shows the
mechanism for locking the commutator handle in the
" Train on line " position after it has occupied the
" Line clear " position, and also shows the mercury
switch, Si, in connection with the releasing circuit.
Figs. 52, 53, and 54 show the various positions of
188 RAILWAY SIGNALLING.
the handle-locking mechanism for the " normal,"
" Line clear," and " Train on line " positions
respectively. The curved lever, L, is raised when
the handle is placed to " Line clear," and a small
stud, shown in dotted lines in Fig. 52, engages with
the projection of the armature of the releasing
coils, B (Figs. 49 and 50), and is held there until
the armature is attracted, which takes place when
the train passes over the rail treadle provided for
FIG. 53. FIG. 54.
closing the circuit. The same movement causes the
shaded disc, F (Fig. 52), to appear at the opening,
N (Fig. 51), in the front of the instrument.
Fig. 51 shows the arrangement of the commutator.
As shown, with the handle in the " Line blocked,"
or normal position, the depression of the plunger
puts the springs a and b in contact, and also springs
c and d, and at the same time breaks contact between
c and e. The current so sent does not affect the
indicators at either station, and the only effect is to
RAILWAY SIGNALLING.
189
ring the bell. When the handle of the commutator
is placed to " Line clear," depression of the plunger
connects springs a and d and b and c, and breaks
contact between c and e as before. The direction
of the current is now reversed, and the lower
semaphore arm at the home station and the upper
semaphore arm at the distant station are lowered,
FlG. 55. — Electromagnetic Mercury Contact
Switch for Controlling Outdoor Signal.
FIG. 56.
and indicate " Line clear." When the handle is in
the midway, or " Train on line," position, depression
of the plunger effects the same combination as when
in the normal position, and the currents so sent
raise the lower arm at the home station and the
upper arm at the distant station to horizontal
positions. Fig. 55 shows a plan and front elevation
igo
RAILWAY SIGNALLING.
of the special mercury switch used in connection
with the electrical control of the starting signal, and
Fig. 56 shows a side elevation of the same. Fig. 57
FIG. 57.— Interlocking of Block Instru- FIG. 58.
ments with Point Fouling Running Line.
shows the method of locking the levers of fouling
points, etc., with the handle of the block instrument
in the "Line clear" and "Train on line" positions.
Conversely, the handle of the block instrument is
RAILWAY SIGNALLING.
locked in the " Line blocked," or normal position,
when these levers are being operated.
Figs. 58, 59, and 60 show the operation of the
electrical control of the starting signal, and Fig. 61 is
a diagram of the connections for one complete block
circuit.
The operation of the instruments for signalling is
FIG. 59.
FIG. 60.
very similar to that of some of the instruments
already described, and need only be referred to very
briefly. The " Is line clear," or equivalent signal,
is given from the sending end with the handle in
the " Line blocked " position. If the signalman at
the receiving end is in a position to accept this
signal, he first moves the handle of his instrument
to the " Line clear " position, and gives the appro-
IQ2
RAILWAY SIGNALLING.
Handle Releasing Jreacttv
Signs/ Hepfacrr'g Trtadte-^ \
7
RAILWAY SIGNALLING. 193
priate accepting signal. The semaphore arms are
lowered at both stations, as already described, by
the accepting signal, and remain in this position,
indicating " Line clear," until further signals are
exchanged. It will be noted that, owing to the
locking of the handle of the instrument by the
mechanism shown in Fig. 50, the ability to place
the handle to " Line clear " is proof that the
previous train has passed over the handle-releasing
treadle, and owing to the interlocking of the block
instrument handle with the levers controlling fouling
points, the ability to move the handle from the
" Line blocked " position is proof that the line is
clear of shunting or similar operations. Further, the
act of placing the handle to " Line clear " raises the
curved lever, L, until it engages with the armature
of the releasing coils. Once in this position, the
locking mechanism prevents it being replaced in
the " Line blocked " position until after the arma-
ture of the releasing coils has been moved. This,
of course, under normal conditions, is done by the
passage of the train over the treadle, but it should
also be noted that the passage of a train over the
treadle during the time the handle is to " Line
clear " will not actuate the armature of the releasing
coils, owing to the switch, S^ being open in that
position. Sj is only closed when the handle is in
the " Train on line " position. The lowering of the
upper semaphore arm at the sending end causes a
local current to be established, which passes from
the battery, D, through the switches, S and S2, to
the controlling electromagnet on the starting signal.
IQ4 RAILWAY SIGNALLING.
Under normal conditions — i.e., when the signal
arm and the lever working it are both in the " on "
position — the armature of the electromagnet on the
signal is kept up to the poles, as shown in Fig. 58,
and the continuity of the circuit is maintained in
this position only. When the signal lever is put
in the "off" position, this mechanical support is
withdrawn, and if there is no current passing through
the coils of the electromagnet the armature will fall,,
and the apparatus will occupy the position shown
by Fig. 60. If, however, the local current through
S, S2, D has been previously established, the armature
is held by the electromagnet, and the action of the
balance weight on the levers and links allows the,
arm to assume the "off" position as in Fig. 59. If
a break occurs anywhere in the local circuit during
the time the signal lever is " off," and the balance
weight occupies the position shown in Fig. 59, the
armature is freed, and, being unsupported mechani-
cally, falls into the position shown in Fig. 60 ; the
relative weights of the signal arm and the central
lever carrying the rod being sufficient to effect this
movement. An examination of the local circuit
shows that it may be broken at three points — viz.,
at S, S2, and at the signal. If the upper semaphore
arm is raised, the switch S will break the local
circuit. This action must take place when the
signalman at the receiving end acknowledges the
" Train on line " signal, and it therefore follows-
that the signal arm cannot remain at "off" after
the " Train on line " signal has been acknowledged,,
although the lever working the arm has been left in
RAILWAY SIGNALLING. IQ5
the "off" position. Hence we see that the signal-
man at the sending end is not only dependent upon
the signalman at the receiving end for the release
of the starting signal, but the latter will replace it
if the former neglects to do so. It is, however, by
no means impossible for the signalman at the send-
ing end to obtain the " Line clear " indication for a
train, and, from forgetfulness, neglect to forward the
" Train on line " signal. Under such circumstances
the signal would remain at " off," if no other devices
than those described were in operation. A further
examination of Fig. 61 will show that the electro-
magnet of S2 is in connection with a second rail
treadle, through the same battery as is used for the
circuit S, S2, and signal electromagnet. If this-
circuit is closed, the switch S2 is reversed, and,
breaking the circuit through the signal electro-
magnet, allows the arm to assume the " on " position.
Although the closing of this circuit may be only
momentary, it will be seen from Fig. 61 that the
reversal of S2 has the effect of diverting the current,
previously passing through the signal electromagnet,
through the electromagnet S2, and so maintains the
reversed position of the latter until the indicating
semaphore arm is raised, when, the switch S being
open, the circuits from the battery, D, are broken,
and S2 resumes the position shown in the diagram
of connections, and is ready for another train.
From the description it will be evident that the
signalman at the receiving end is master of the
situation. The signalman at the sending end cannot
lower the signal for a train to proceed until he has
13*
ig6 RAILWAY SIGNALLING.
received "Line clear" from the station ahead; and
if he does not himself replace this signal at the proper
time it is done by the acknowledgment of the " Train
on line " signal from the receiving end ; or, in the
event of the train being sent forward without this
signal being given and acknowledged, it is done by
the action of the train passing over the treadle, and
the signalman is unable to again lower it until the
indicating semaphore has been raised and lowered
again. When the " Train on line " signal is received
from the sending end of the section, the signalman
at the receiving end places the handle of his instru-
ment in the midway position, which is the only
movement possible, and acknowledges the signal in
accordance with the code. The movement of the
handle locks it in the midway position, and it cannot
now be moved in either direction. The switch ST
is closed by the same action. On the arrival of
the train at the receiving end of the section, it
passes over the treadle in connection with the battery
G, and a current is established through the switch
S, and the handle-releasing coils. The armature is
attracted, and allows L to drop into the position
shown in Fig. 52. The handle of the instrument
is now free, and may be placed in either the " Line
blocked " or the " Line clear " positions. The
proper position for it is, of course, the " Line
blocked " position, and when this is done the
" arrival " signal is given according to code.
This system is an interesting example of the
possibilities of block working, and also of the diffi-
culties to be overcome before even a moderate check
RAILWAY SIGNALLING. IQ7
can be established over those engaged on working
traffic. The elaborate precautions taken to ensure
the replacement of the starting signal after it has
fulfilled its duty, and to ensure its not being used
to send a train forward prematurely, mark the starting
signal as being of the utmost importance in the
estimation of the designer. There can be no doubt
that the position of this signal is of great importance,
but the history of railway accidents shows that its
being in the " on " position has not always acted
to prevent a train from passing into the section it
protects, with disastrous results in some cases. The
apparatus in connection with the starting signal has,
obviously, been designed solely with the object of
checking the action of the signalman, and provides
in no way against the possibility of error on the
part of that other important factor in the problem,
the engine driver. Further consideration of the
arrangements for unlocking the starting signal suggests
the possibility of this being done through accidental
contact between the line wire and another working
wire along the route between the two ends of the
section.
The next important point in the system is the
locking of the instrument handle, at the receiving
end, until the train has passed over the treadles in
connection with the releasing coils. It will be
noticed (Fig. 53) that the operation of locking
commences when the instrument has been prepared
to give the " Line is clear" signal, and is completed
when the " Train on line " signal has been acknow-
ledged. Once the handle has been moved to the
ig8 RAILWAY SIGNALLING.
" Line clear " position it cannot, in the course of
ordinary working, be replaced to "Line blocked"
before the treadle is operated. An "Is line clear"
signal or " Train on line " signal cannot therefore be
cancelled, in the sense that all the apparatus con-
cerned may be returned to the " Line blocked "
condition without special arrangements being made
for releasing the handle at the receiving end of the
section. Theoretically, the " Train on line " signal
should never require cancelling, but there are occasions
when it may be necessary. Cancellation of the " Line
clear " signal is of much more frequent occurrence,
more especially in connection with junction working
and at points where traffic is lifted and left. In the
case of a junction, such as is shown in Fig. 21, the
signalman there might offer the "Is line clear " signal,
and have it accepted, from two or even the three
advance cabins, in which case the three starting
signals would all be unlocked electrically, and any
one of them might be used. Such a case as is here
supposed is by no means far-fetched. Where signal-
men at junctions have to deal with a heavy mixed
traffic they often have to rely upon the whistles
given by the driver, and when the wind is in a
contrary direction it is by no means easy to distin-
guish the number and length of the whistles given ;
and since the " Line clear " signal must be obtained
before the arrival of the train at the cabin at the
sending end in order to prevent delay, the cancelling
signal becomes of some importance. Further exami-
nation of the handle-locking mechanism shows that
it is not impossible for the signalman at the receiving
RAILWAY SIGNALLING. IQQ
end to (a) replace the indicating semaphore arms to
"Line blocked" in the interval between his giving
the " Line is clear " signal and receiving the " Train
-on line" signal; (b) give the "arrival" signal to the
sending end at any time after receiving and acknow-
ledging the " Train on line " signal, but the locking
of his instrument handle would prevent him from
accepting a second " Is line clear " signal. The
apparatus provides indications representing " Line
clear," "Train on line," and "Line blocked," at
the receiving end of the section, but does not dis-
tinguish between "Line blocked," and "Train on
line" at the sending end."
Sykes's Three-Wire, — Another method of locking
the block instruments with the outdoor mechanical
signals is shown by Figs. 62-71, which illustrate
Sykes's three-wire system, familiarly known as the
S.Y.X. system. As in Winter's and Saxby and
Farmer's systems, the principal object aimed at is
the control of the starting, or advance, signal at the
sending end of the section by the signalman at the
receiving end, but it is distinguished for the extreme
simplicity of the electrical apparatus and for its
departure from the usual design of such apparatus.
The system provides a combined locking and indi-
cating instrument for each line of rails, each instru-
ment being provided with a separate line wire ;
separate bell communication between the ends of each
section by which all signals other than those indicating
the condition of the line for the time being are sent ;
a mercury contact rail treadle placed near the starting
signal to release the locking arrangements at the
200
RAILWAY SIGNALLING.
proper time ; and an automatic signal-arm replacer,
fixed on the starting signal, which is also worked in
connection with the rail treadle.
The general arrangement of the block indicator is
shown by Fig. 62. It consists, as will be seen, of
two distinct portions. The upper part containing
the small semaphore arm constitutes the block indi-
cator for one line of the advance section ; whilst the
FIG. 62.— Sykes's Block Indicator.
lower part contains the mechanism for interlocking;
the instrument with the mechanical signal at that
place, the electrical apparatus by which the mechanical
signal at the rear cabin is released for use, and the
indicators of the condition of the rear section of the
same line. One portion of each instrument is, there-
fore, worked from the advance cabin, and the other
portion is worked to the rear cabin, and the indica-
RAILWAY SIGNALLING.
20L
tions of different parts of one and the same instrument
give to the signalman information of the condition
of both sections so far as one set of rails is concerned.
The construction of the semaphore indicator is
shown by Fig. 63. The position of the arm is
horizontal when no current is passing through the
coils of the instrument, and in this position the arm
indicates the equivalent of " Train on line." When
FIG. 63.
the section is clear of trains on the line of rails
represented by the indicator, or of shunting opera-
tions at the receiving end of the section, the arm is
held in a diagonal position by a permanent current,
and indicates in this position the equivalent of " Line
blocked." A reference to Fig. 71 will show that the
position of the arm is controlled by the signalman at
the receiving end of the section, and its indications
are in no way dependent upon the actions of the man
202 RAILWAY SIGNALLING.
at the sending end of the section. Fig. 64 is a
perspective view of the locking mechanism in the
lower part of the instrument. Fig. 66 is a front
FIG. 64.
-elevation, and Figs. 65 and 67 are left and right
elevations of the same respectively, but the relative
positions of the various parts of the apparatus are
•different in Fig. 67 to the positions the same parts
RAILWAY SIGNALLING.
203
occupy in^Figs. 65 and 66. The apparatus consists of
a plunger, P, actuated by the knob, R, the polarised
electromagnet, H, a switch, T, the lock bars, M, n, O,
and the rods, L and N, in connection with the starting
signal mechanism. The plunger, P, at any block
FIG. 65.
cabin makes connection between the spring, S2, and
the battery studs i and 2 (Figs. 66 and 71), and sends
a current through the polarised electromagnet at the
rear cabin in such a direction as tends to weaken the
attraction of the permanent magnet upon the soft-iron
204
RAILWAY SIGNALLING.
armature. The armature, A (Fig. 65), is carried by
one arm of a bell crank, C, the vertical arm of which
carries a small friction wheel. A pin projecting from
the vertical arm causes the latter to be^ acted upon
by the strong spring, F (Fig. 66), which tends to
FIG. 66.
separate the armature from the poles of the electro-
magnet. Under normal conditions A is held by the
attraction of the polarised electromagnet, and the
release is effected by passing a current of suchfstrength
and direction as will allow the spring, F, to overcome
the diminished attraction of H. The switch, T, is
RAILWAY SIGNALLING.
205
used in connection with the one-cell battery shown
in Fig. 71.
This battery is used simply to hold the semaphore
indicator at the rear cabin in the "off " position when
the section is clear of trains on the line of rails it
represents, and no operations involving the fouling
of this line are being carried out. The lever, L, is
pivoted at c (Fig. 68), and carries at one end of the
arm the lock rod, d, for the signal lever, and at the
other end the friction wheel, 6. The continuation
of L within the case of the instrument carries a light
2O6 RAILWAY SIGNALLING.
frame, on which is painted " free," " locked " (Fig. 66).
These indications appear, in their proper order, at
the upper opening of the instrument case, and indicate
to the signalman the condition of the starting or other
signal connected with L. Within the case, L carries
the projection, g (Figs. 65 and 67), which rests upon
the friction wheel of C, as shown by the full lines in
Fig. 65. Under the instrument L carries the parallel
bolt, k, which, passing into the interior of the instru-
FIG. 68.
ment, engages with the horizontal arm of C and raises
the armature, A, into contact with H, when the
motion imparted to L by the movement of the signal
lever is upward. When the projection, g, rests upon
the friction wheel of C the weight of L is supported
by the latter, and the short arm pivoted at c (Fig. 68)
is in such a position as to lock the signal lever in
the "on" position. If the armature, A, is released
L is lowered until the friction wheel, b (Fig. 68)y
RAILWAY SIGNALLING. 2O7
rests upon the semi-circular rim of the double bell
crank, and by doing so lifts the lock rod, d, into
the position shown by Fig. 68 and releases the lever.
At the same time the word " locked " disappears, and
"free" takes its place at the upper opening of the
instrument, indicating to the signalman that the
lever is free to be placed in the "off" position.
The tongue, t (Fig. 68), working on the same centre
as the double bell crank, is loose, and works in a
V groove on the' vertical face of the- crank. When
the lever is placed in the " off" position t passes
under the friction wheel, 6, and raises L, and, in
consequence, the armature, A, is raised into contact
tj.
FIG. 69.
with the poles of H by k and held there. The word
"free" disappears and "locked" takes its place at
the upper opening of the instrument, indicating, in
conjunction with the position of the signal lever,
that the latter is locked in the "off" position.
Consideration of Fig. 68 will show that this is
really the case, and the signal lever cannot be fully
replaced in the " on " position until the armature,
A, has again been released. This release takes
place when the train passes over the rail treadle
near the signal actuated, and the word " free " again
replaces " locked " at the opening in the instrument
case. In replacing the lever in the " on " position.
208
RAILWAY SIGNALLING.
t again raises L and the armature. The latter is
retained by H, and the former by projection, g,
resting on the friction wheel of C, and, so far as
the electrical control of the signal is concerned, the
apparatus is ready for a similar cycle of operations.
The word " locked " again appearing at the opening,
FIG. 70.
indicates the locking of the signal lever in the " on "
position. The slotted lock bar, M, carries on one
side the swinging lever, O (Figs. 65, 66, and 67),
and on the other side a second slotted bar, n (Fig. 66).
As seen in Figs. 65 and 66, O is resting on the top
of the rod, N, which is in the position it occupies
RAILWAY SIGNALLING. 2OQ
when the signal lever is in the "on" position. If
the plunger, P, is depressed under these conditions,
the lever, O, is pressed back until it clears N, and
the lock bars, M, «, O, drop into the position shown
by Figs. 64 and 67 when the plunger is released.
The mechanical result of this operation is to exhibit
" Train on " at the lower opening of the instrument,
and to place the slots of the lock bar, M n, in such
positions, relatively to the plunger, that the latter
cannot be again depressed until certain operations
have been performed. The electrical results follow-
ing the depression of the plunger are the breaking
of the one-cell battery circuit by the fall of M (up-
line instrument at " C," Fig. 71), and the consequent
raising of the semaphore arm at the rear cabin to
the horizontal position (up-line instrument at " B,"
Fig. 71), and the unlocking of the armature, A, at
the rear cabin, by the current established by the
contact of the spring, S2, with the battery studs I
and 2 (Fig. 71). A glance at Fig. 68 will show
that when the signal lever is pulled into the "off*
position, the rod, N, is drawn downward, and if
the plunger has been previously depressed N will
slide over the sloping face of O (Fig. 67), pressing
it back meanwhile, until it reaches its lowest point,
when O being free of N, again takes up a position
immediately over the latter. In replacing the signal
lever in the " on " position, the upward movement
of N raises M, », and O into the positions shown
in Figs. 65 and 66, when the plunger is available
for use again. If it should be required to place the
signal lever in the " off" position, without previous
14
210
RAILWAY SIGNALLING.
RAILWAY SIGNALLING. 211
use of the plunger, as would be the case for a train
issuing from a relief siding, such as is shown by
Fig. 20, the lowering of N simply lowers M, n, and
•O into the position previously described, when, as
before, the signalman is unable to depress the
plunger in order to allow a train to leave the rear
end of the section. It is evident therefore that a
necessary condition of the use of the plunger is that
the signal lever controlling entrance to the advance
section shall be in the "on" position.
In addition to the operations described, the placing
•of the signal lever in the "off" position breaks the
connection of the locking electromagnet with the line
wire to the advance cabin, and connects it with the
special circuit and battery to the rail treadle (up-line
instrument at " C," Fig. 71). Remembering that the
apparatus locks the signal lever in the " off," as well
as in the " on " position, and that " locked " appears
at the upper opening at this stage of the operations,
it will be seen that it is impossible to release the
armature, A, by a current from the advance cabin
quite irrespective of the locking of the plunger at
that place consequent upon its use to release the
armature in the first instance. In addition to the
apparatus described, the system includes a mercury
contact rail treadle (Fig. 69), in which the contacts
are made by the tilting of the vessels containing the
mercury, consequent upon the depression of the rail
acting through a plunger on the short ends of two
levers, to the longer arms of which the vessels con-
taining the mercury are connected. There is also an
.automatic arrangement for replacing the signal arm
14*
212 RAILWAY SIGNALLING.
in the " on " position by the passage of the train'
over the treadle, irrespective of the position of the
lever operating the signal under normal conditions.
The automatic signal replacer is shown by Fig. 70..
The rod actuating the signal is attached directly to
the upper part of the box containing the apparatus,,
and the slide bar, /, is worked by the lever from the
cabin. The normal position of the sloped upper end
of / is under the lever /, in which case the slot on
the upper surface of / engages with the slot on the
lower surface of p, the latter being pulled into a
vertical position by the spring, s. Under these
conditions the box and the apparatus it contains
work with the movement of the signal lever, the
upward movement being transmitted from / through,
the levers, / and />, to the case and the rod working
the arm, and the downward movement by the greater
weight of the box and rod as compared with that of
the signal arm outside the centre on which it turns.
If the electromagnet is energised, the hammer, h, is
released and falls upon the rod, i, and disconnecting
the two slotted levers, / and p, allows the box to fall
and place the arm at danger. The wheel, w, is
pressed outwards by the sloping end of /, and causes
p to turn on its centre. The A-shaped projection
of p engages with the wheel, wlt on h, and causes
the latter to assume its original position. When the
signal lever is placed in the " on " position, the
slide, /, is lowered, and / engages with p. The
apparatus is then ready for further use.
Consideration of the illustrations, and description
of the functions of the various pieces of apparatus
RAILWAY SIGNALLING. 213
forming the system, will show that the objects aimed
at in the design do not differ materially from those
of other systems, but the arrangement of the
apparatus is novel, and the electrical devices are
of the simplest possible character. Fig. 71 is a
diagram of the connections for a simple block section
such as is shown by Fig. 19 ; but the block bell
•connections are omitted, as they differ in no way
from those described in connection with the three-
wire single-needle system, and are entirely independent
of the block indicators and locking apparatus. The
paths of the currents will be easily traced from Fig. 71,
which is drawn to represent the positions of the
apparatus on the assumption that a train is passing
through the section from "B" to "C" on the up
line. This train has been accepted by D as shown
by the horizontal position of the semaphore arm of
the up-line instrument working from D ; and the
change in the connections of the electromagnets
shows that the starting signal at " C " is " off,"
whilst the position of the armature and the " locked "
indication exhibited show that the signal lever is
locked in the " off" position. The indication "Train
•on" at "C" shows that the plunger has been used
to liberate " B's " signal, and is itself now locked.
The position of " B's " electromagnet connections
and the " locked " indication exhibited show that
the train has passed over the treadle at " B," and
that the signal lever has been placed in the " on "
position ; whilst the position of the switch, T, at
*' B " indicates that the train has not been cleared
Jback to " A," or that " B " has undertaken shunting
214 RAILWAY SIGNALLING.
operations involving the fouling of the running line
inside the starting signal. The switch, T, in the
position shown at " B's " up-line instrument would
embrace the plunger rod and prevent it being used
inadvertently.
The novel arrangement of the battery used in
operating the plunger is intended to minimise the
chance of inconvenience being caused by failure of
the battery or its connections. The batteries act in
parallel when in use, and the connection to the
battery terminals in the instrument are duplicated.
Of course the chance of failure with two batteries,
each capable of doing the work, is much less than
with one battery alone. As shown in Fig. 71, how-
ever, failure of the battery earth would render both
batteries inoperative, and it would therefore be
necessary to carry the duplication of connections to>
the fullest extent in order to secure all the advantages-
accruing from the use of duplicate batteries.
Fig. 71, as stated, represents the arrangements for
working the simplest possible block section only. For
junction working the arrangements have necessarily
to be more complex. For such a junction as Fig. 21
represents, releasing treadles are required for each of
the diverging lines, and each treadle must be capable
of working the same instrument. For the lines
converging at the junction the plunger used to liberate
the signal at the rear cabin of any one of the
converging sections is arranged to be free for use
only when the points have been set for a train coming
from that direction. This, of course, with the usual
signal and points interlocking, would mean the control
RAILWAY SIGNALLING. 215
of each plunger by the "home" signal for that section,
and would ensure all other signals for lines converging
there being at danger. Only one treadle would be
required for trains coming from any of the converging
lines. The arrangements for special cases like junction
working, will, however, depend greatly upon local
conditions, and it is not possible to give more than
the barest outline of the arrangements for such cases.
Circumstances will, however, sometimes arise in
apparently simple cases which would seem to indicate
the necessity for more elaborate arrangements than
are shown by Fig. 71. Fig. 20 is a very simple block
station, but if we assume the arrival of a train at
that place with a bare time margin in front of a
more important train, the necessity for shunting the
first will arise. If the releasing treadle is placed at
or in advance of the " advance " signal, and there is
only one treadle, the train which is to be shunted
will require to actuate the treadle — in which case it
may actually be in the advance section — before the
starting signal (which is assumed to have been
lowered) can be replaced. If the starting signal has
not been lowered, the signalman knowing the train
will require shunting, then some further arrangement
will be required to release the plunger in order to use
it to enable the second train to advance when the
first has been safely shunted. Further consideration
of the same case would suggest the possibility, with
only the arrangements described, of the shunted train
being afterwards allowed to proceed to the " advance "
signal, and of a second train being brought into its
rear from the rear cabin, since the starting signal
2l6 RAILWAY SIGNALLING.
being " on " the plunger would not be absolutely
locked. Of course, the case cited would be readily
met by establishing control of the instrument with
the siding points levers, or even control of the switch-
handle, T, with the same lever, but the case is given
simply to show that in apparently simple cases the
arrangements for complete safety against the results
of carelessness or neglect must be more elaborate than
would seem necessary at first sight. Further con-
sideration of the apparatus suggests the possibility of
the starting signal being unlocked by contact of the
block instrument line wire with another working wire
on the same route, and this, in combination with
other circumstances not altogether unknown in rail-
way work, might result in two trains being in the
section on one line of rails together.
This, of course, is by no means peculiar to the
instrument just described, but is common to all
classes of instrument in which the movements
resulting in the release of locking apparatus or the
setting of the indicators in their more important
positions, are due to one person only. Of the
various classes of instrument already described,
only two, Preece's and Winter's — two instruments
which have much in common — take notice of the
effect likely to be produced in this way. Whilst
the danger of serious results from such causes is
very much less now than a few years ago, owing to
improved construction of lines and greater vigilance
in maintaining them in an efficient condition, yet
line contacts are not entirely things of the past,
and, as has already been remarked, the history of
RAILWAY SIGNALLING. 217
railway accidents is full of instances of curious com-
binations of circumstances, which would appear as
most improbable of simultaneous occurrence. In
this system, as in others of a similar kind, cancel-
lation of a signal which has resulted in the pre-
paration of the line for the passage of an approaching
train can only be done by special means, which may
or may not be immediately available for use by the
signalman, and the use of which is an infringement
of the automatic character of the apparatus. In
some cases cancellation is directly prohibited, and
the replacement of the apparatus in its normal posi-
tion is made by the next train in that direction, it
being worked through the section at " caution," in
consequence of the defect in the apparatus. Prob-
ably such a regulation would do much to promote
care in the dispatch of signals asking for the clear-
ance of apparatus for an approaching train, seeing
that every lapse and the consequent delay would
have to be fully explained.
This system, like others, whilst providing for the
automatic clearing of the section by the passage of
the train itself, makes no provision for automatic
notification of the entrance of the train into the
section at either of the cabins controlling it. Yet,
surely, if it is undesirable for the signalman at the
receiving end of the section to trust entirely to his
observation for guidance in clearing a section, it
must be equally undesirable for him to trust to the
signalman at the sending end for notification of
the entrance of a train ; and circumstances might
easily arise where such independent notification
218
RAILWAY SIGNALLING.
would be of the utmost value to the signalman at
the receiving end of the section in the event of an
unauthorised train entering a section through the
prevalence of fog or other similar cause.
Swingbridge Arrangements. — Fig. 72 represents
a portion of the main line of one of the through
routes to the North. Two important lines from the
north and east converge upon a swingbridge crossing
FIG. 72.
a navigable river. All four sets of rails are carried
over the swingbridge, but the two " up lines " and
the two "down lines" are "bunched," and the
bridge is little wider than would be required for the
ordinary double line of rails. At the south end of
the bridge the lines widen again owing to the station
platform lines being distinct from the running lines.
Consideration of Fig. 72 will show the necessity for
RAILWAY SIGNALLING.
extra precautions in working this section of the line,
owing to the possibility of accident resulting from
the fouling of the lines at the north end of the
bridge, and from the presence of the bridge itself.
This portion of line is divided into two block
sections, A B and B D (Fig. 72) ; C is a cabin on
the swing portion of the bridge in which is installed
the control of the hydraulic machinery for operating
the bridge for the passage of river traffic, but
although it is provided with electrical apparatus,
connected with B, by which the operation of the
bridge is controlled, it is entirely dissociated from
the block working of the section, B D, in which it
is situated. The signalman at B is in this case the
person controlling the operation of all traffic on to
the bridge from either direction ; and he also controls
indirectly the river traffic by means of the apparatus
by which the bridge is locked in the position for the
passage of railway traffic.
The line is worked by three-wire single-needle
block instruments, to which is added an adaptation
of Sykes's lock and block to the indicators for the
two up lines between D and B. The operation of
the bridge is controlled by Sykes's instruments alsor
and the handles of the two down-line instruments
are connected with the signal locking at B.
Fig. 73 is a diagram showing the wires used for
signalling, and locking between A and B, B and D,
and B and C. The construction of the up-line block
instruments at B, working to D, is shown by Fig. 74,
and the additional apparatus to the corresponding
instruments at D is shown by Fig. 75. So far as
220
RAILWAY SIGNALLING.
the block instruments themselves are concerned, they
differ in no way from others previously shown, and
the novelty of the arrangement consists in the addition
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FIG. 73.
LJ1
PLU/TCE/* LOCKS
E.E.
FlG. 74. — S N Instrument with Sykes's Plungers.
•of the lock bars M n O, the continuation of the lever
L, and the plunger P (Figs. 65, 66, 67), for specific
purposes. Practically, the apparatus shown by Fig. 64
RAILWAY SIGNALLING.
221
is split into its two component parts, the plunger and
its locking apparatus being added to the " up " line
FIG. 75.— S N Instrument with Sykes's Signal- Locking Apparatus.
This must be
rsrsfftf be fora
depress/no
(finger y
FIG. 76. Bridge- Locking Apparatus.
instrument at B, and the signal locking, or receiving
portion of the complete instrument, consisting of the
322 RAILWAY SIGNALLING.
polarised electromagnet, armature, etc., being added
to the corresponding instrument at D. The special
bridge-locking apparatus is shown by Fig. 76, the
arrangements of apparatus at C being identical with
those at B. The apparatus is practically the same
as is shown by Fig. 64, with the exception that S1
and the other connections for the semaphore indicator
are omitted as the latter is not used. The handle of
the switch, T (Figs. 65 and 67), is retained, but it
is merely mechanical in the present arrangement.
The general arrangement of the instruments at B
relatively to the signal levers working the signals,
points, clearance bars, and inter-cabin control, is
shown by Fig. 77, together with the interlocking
of the "down" line instruments to A with the lever
locking. Fig. 78 shows the electrical connections
for the locking apparatus between B and C and B
and D. The connections of the block instruments
are not given, for reasons already adduced. It will
be observed that the locking and indicating apparatus
of the additions to the up-line block instruments at
B and D are operated by one lever instead of by
two, as in the ordinary arrangement of Sykes's
instruments for block working, and this of course
follows from the separation of the different parts.
The levers, N, operating the plunger locks at B
are connected together, as shown diagrammatically
in Fig. 77, so that only one plunger can be used
at once. The plunger of either instrument can only
be depressed after the lever operating the rod, N,
of that instrument has been moved into position
for a train to approach on that line, and as this
RAILWAY SIGNALLING.
223
lever is interlocked mechanically with other levers
necessary to that particular line, it follows that the
road must be completely set at B before either of
V'ffje Stop. ......
Up Platform. .-.;..
ToUpMiin •
Control River Signal
Spare
Main Rmg...._
I** OH- MIL...
Bridge Lock
x
From Poirts'H'. From?
Lock Bar N. 16. -si
Clearance Bars. . . <^
Spare
Spare
Spare
lo^H" Advance.. .
To"H"Home
Step from Down trram
Distant Irom DownHim p t
To "Y"Advance.
Home. . .
Down Platform Dist*
224
RAILWAY SIGNALLING.
the electrical locks at D can be released, and even
then only the lock controlling the signal for one
particular line can be released.
The signals i 2 (Fig. 72) at D are those which are
under electrical control from B. The levers, at D,
working these signals are also connected, so that
FIG. 78.
the operation of the lever for one of them locks
the rod, L, of the other instrument, so that it
cannot be released by a current from B, however
sent. This is an additional check against fouling
at the north end of the bridge, and is quite inde-
pendent of the action of the plunger locks and the
connection existing between the two rods, N, at B.
RAILWAY SIGNALLING. 22$
As will be seen, B effectually controls the approach
of trains from D, and so long as the apparatus is
in order and the mechanical signals are obeyed it is
impossible for trains to foul each other at the north
end of the bridge. Fouling between a train passing
from B on the " H " line and a train approaching
B on the " Y " line is provided against by the
mechanical interlocking of the signal and point levers.
In addition to the provisions described for ordinary
working over the " bunched '* part of the block
section, B D, provision has to be made for blocking
all four lines from both directions during the time
the bridge is open for river traffic. The up lines
from D to B have been described. B controls the
down-line signals at A by lever 15 (Fig. 77), and this
lever is interlocked with the handle, Mx, which, when
placed vertical, causes the down-line instruments at
A and B to indicate " Train on line." Hence, so
long as the mechanical signals are obeyed, the bridge is
protected against the approach of trains from A on
the "down" line.
When it is necessary for the bridge to be opened
for river traffic, C notifies B by the code arranged
for use with the separate bell circuit. When the latter
is ready, after performing the operations indicated for
the protection of the down line, etc., he operates the
bridge lock lever (13, Fig. 77) and raises the lever Px
by hand, and by depressing the plunger unlocks the
instrument at C, enabling him to make the pre-
liminary arrangements for opening the bridge. C then
raises the rod, Pl9 of his own instrument, and by
depressing the plunger locks the lever 13 at B in the
15
226 RAILWAY SIGNALLING.
open position, and thus prevents it being inadvertently
put back. Under these conditions C is master of the
situation, and B is unable to undertake any operation
involving the approach of trains from either A or D.
When the bridge is again ready for railway traffic
the operations are reversed, and C becomes dependent
again upon B for permission to operate the bridge on
the succeeding occasion.
Blakey and O'Donnell. — Fig. 79 represents,
diagrammatically, Blakey and O'Donnell's method
of interlocking and automatic signalling as adapted
for use with single-needle instruments. As will be
seen, the design requires the use of an additional
line wire between the treadle at A and B.
The hammer, h, of the signal replacer, G (Fig. 79),
is held off by the rod i (Fig. 70) when a current
passes through the coils of the replacer only. The
arm, therefore, normally stands at danger through
the rod f not engaging with p, and the latter with e.
Consideration of Fig. 79 will show that the " Line
clear " current from B passes through the coils of
R, and, in consequence, the armature of the latter
makes contact at /. If the signal lever is now
pulled into the "off" position, the replacer circuit
is completed at K, and the battery B3 sets up a
current through G, which holds the hammer, h
(Fig. 70) in position, and allows f to gear with the
mechanism, and to lower the signal.
When the train passes over the treadle at A, the
battery B4 at B energises the relay, R, the treadle
at B forming a closed circuit normally. The arma-
ture of R! is attracted, breaks the circuit of the
RAILWAY SIGNALLING.
227
-H
15=
228 RAILWAY SIGNALLING.
instrument battery, B2, and at the same time com-
pletes the circuit of B6 through the instruments at
B and A, and through the coils of R at the latter
place.
The needles now indicate " Train entering section,"
and the armature of R breaks the contact at c. The
signal replacer circuit being broken, the hammer, h
(Fig. 70) being no longer held up, falls upon i, and
puts the signal to danger.
The current sent by the depression of the treadle
at A continues only during the period of such depres-
sion. An examination of the connections at B will
show that the movement of the armature of R, under
the action of the treadle current, completes a second
circuit through Rlt the armature, and the treadle at
B, which maintains the armature in position for
indicating " Train entering section."
On the arrival of the train at B, depression of the
treadle there breaks the circuit, B4, treadle, and Rlr
and the armature of the latter returns to the position
shown by Fig. 79. The movement of the armature
of R! breaks the circuit of the battery B6, and com-
pletes that of the battery B2.
It will be noticed that the signalmen at B and A
are not actively engaged on the operations necessary
to indicate " Train entering section," since the opera-
tions are performed automatically by the action of
the train passing over the treadle at A. The instru-
ment handle at B may stand in any of the three
positions without affecting the indications during the
time the train is in the section.
Should the signalman neglect to unpeg the handle
-RAILWAY SIGNALLING. 22Q
from the " Line clear " position, it will be seen on
consideration that when the train passes over the
treadle at B the instruments will at once indicate
" Line clear " at both stations, and the signalman
at A will be in a position to pull off the signal
controlling entrance to the section without having
asked permission previous to doing so.
The design affords an intimation to the signalman
at the receiving end of the section of the entrance
of the train into the section he controls indepen-
dently of what may be done by the signalman at
the sending end of the section, and this is a point
•of considerable importance. Another point of some
importance is that neither of the signalmen is in a
position to alter the " Train entering section "
indication. Other points are the control of the
starting or advance signal at A by the signalman
at B, and the automatic release of the circuit by
the arrival of the train at a certain point at the
receiving end.
A similar development of the principle of automatic
signalling is shown by Fig. 80, which represents Sykes
and O'Donnell's system as applied to single-needle
instruments, and which is at present on trial on the
Great Northern Railway at Finsbury Park and else-
where.
The additional apparatus consists mainly of the
polarised relay, R, and the differentially - wound
electromagnets, Rj and R2, the contact, K, controlled
by the position of the lever of the signal controlling
entrance to the section, the treadles, and the Sykes
signal replacer, G. The spring contacts, a at A, and
UNIVERSITY
230
RAILWAY SIGNALLING.
-— ==r==rrrr
--
RAILWAY SIGNALLING. 23!
b at B, are shown in the positions they occupy when
the needles are indicating " Line blocked," as in
Fig. 79. If the handle at B is pegged to " Line
clear " the spring b is caused to break contact at 2,
and if the handle at A is moved from its normal
position the spring a breaks contact at i. The
movement of the spring a is necessary in order to
prevent currents originating at A from having the
same effect upon the relay, R, as similar currents
originating at B are required to have. The move-
ment of b is necessary to ensure against premature
replacement of the armature of R2 to the contact 14
in the event of the signalman having neglected to
unpeg the handle from " Line clear " after the receipt
of the " Train entering section " signal.
The contacts made by the armatures of R, Rx, and
R2 are as shown when the needles are indicating
" Line blocked." A portion of the current originating
at B when the instruments are indicating " Line
clear " causes the contact c of the armature of R, at
A, to be broken. The remainder of the portion of
this current which reaches A is used to deflect the
needle of the instrument. Another portion of the
current set up in pegging the handle at B to " Line
clear " passes through one of the coils of Rj at B,
but strengthens the contact between the armature
and 12. The paths of the " Line clear " indicating
current are shown diagrammatically by Fig. 81, from
which it will be seen that the relay R and the S N
instruments are in parallel at A, and that both these
form a shunt on the coil of Rx at B.
When the " Train entering section " signal is sent
232
RAILWAY SIGNALLING.
on the bell, the signalman at B should peg the needles
to that position. If he does not, however, the passage
of the train over the treadle at A sets up a current
from the battery B3, which, dividing at E3, passes
partly by E: and partly by E2. The part passing by
Ej divides again, one portion passing through R
replaces the armature against c and completes the
signal replacer circuit through 17, G, K (the signal
lever being pulled into the "off" position), c, I, a to
18. The other part passing by Ej passes to 10, the
PATH OF LHU CLEAR
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FIG. 81.
S N instrument coils (deflecting the needle to "Train
entering section "), 9, 4, 3, and 18. These two
portions join at 18 and return to Z of B3.
The part of the current originating at B3 on the
depression of the treadle at A, which passes to E2,
passes further to 5 at B, thence through one coil of
R! (reversing the position of the armature to contact
n), thence to 8, line wire, 18, and Z of B3.
It will be noticed that the reversal of the armature
RAILWAY SIGNALLING. 233
of Rj breaks down the circuit of the battery B2,
which has hitherto been maintaining the " Line
clear " indication, and completes the circuit of the
battery B4.
The current set up at Bs by the depression of the
treadle at A lasts only during the period of depression.
During the time the train is passing over the treadle
at A both batteries, B3 and B4, are in operation.
After the train has passed completely into the section
the work of maintaining the indications and other
necessary operations is performed by B4 alone.
j
(K
rf 5"
,*
' ----- kl« ---- >. ------ '? COILS
f 1
I"
ii-
FIG. 82.
Fig. 82 is a diagrammatic representation of the
path of the current originating at B4 during the time
the latter is acting alone. As will be noticed, the
direction of this current through the various pieces
of apparatus is the opposite of that of the " Line
clear" current. Further, the replacer circuit at A
is also traversed by a portion of the " Train entering
section" indication current.
On the arrival of the train at the treadle at B,
234 RAILWAY SIGNALLING.
a fresh current is set up from B4 by the depression
of the treadle. This current divides, part passing
through one coil of R2 and part through one coil
of Rj. The result is to replace the armature of R
to contact 12, and to place the armature of R2 to
contact 13. The result of these two operations is
to remake the circuit of B2 at 12 and to complete
a local circuit under certain conditions through C
of B2, b, R2, 13, 16, Z of B2. The condition to be
observed for the completion of this local circuit is
that the handle of the instrument at B shall be in
such a position as to complete the contact between
b and 2 — that is to say, the handle must not be in
the " Line clear " position. The current thus set
up through R2 replaces the armature of the latter
to contact 14, and sets the apparatus in position
for use for further traffic.
Besides the operations described, the apparatus
acts in a most ingenious way to prevent the signal
controlling entrance to the section from being lowered
when either the " Train entering section " or the
" Line blocked " indications are being exhibited.
The form of replacer is shown by Fig. 70. As
already explained, the arm is lowered by the rod /
engaging with p, and being locked by the lever, /,
the hammer, h, when no current is passing through
the electromagnet, engaging with the lever attached
to the armature, and being held by it. Returning to
Fig. 80, we find that the " Line clear" current from
B breaks the replacer circuit at c, and, consequently,
no current can pass through G, even when the con-
tact, K, is made by the lever being pulled into the
RAILWAY SIGNALLING. 235
" off " position. On the train passing over the treadle
at A, the contact at c is made by the currents set
up from B& and B4, and a current passes from Eg
through G, K, c, and 18, which operates the replacer
and puts the signal to danger. If the signal lever
is replaced in the "on" position completely, the
current through G will be broken by the opening of
the circuit at K. The rod / (Fig. 70) will then be
in its lowest position, and under normal circumstances
the replacer would be geared for lowering the signal
at any future time. It will, however, be noticed that
K is operated, not by the mere replacement of the
lever, but by the lowering of the catch of the lever.
The circuit through G is therefore complete until
the lever is fully in position and the armature of
the replacer does not retain the hammer, h, and the
rod / cannot engage with p. Further consideration
will show that any attempt to lower the signal by
subsequent movements of the lever will be ineffective
owing to the closing of the contact K by the lifting
of the catch of the lever setting up a current which
energises the electromagnet of the replacer during
the whole time the contact, c, is maintained. Further
consideration will show that if the lever of the signal
is replaced in the " on " position during the time the
train is in the section, it will be necessary to pull it
into the "off" position before the mechanism of the
replacer will engage so as to allow the signal to be
lowered.
Summary of Objects.— The objects aimed at in
the designs shown by Figs. 79 and 80 are obviously
identical, and may be summarised as on the next page :
236 RAILWAY SIGNALLING.
(a) Effective control of the signal controlling the
entrance to the section by the signalman at the
: .advance station.
(b) Automatic intimation of the actual entrance of
a train into the section.
(c) Automatic clearance of the section.
Whilst these are the chief objects of both designs,
they differ considerably in the means by which they
are obtained, and slightly in the degree of perfection
attained by the apparatus.
Fig. 79 may be called a five-wire system since that
is the number of line wires required to operate the
apparatus in its proper sequence for a double line of
rails. Fig. 80 accomplishes the work with three line
'wires, and four batteries as against five batteries
required by Fig. 79. Fig. 79 is, moreover, defective
and inferior in that it does not necessitate independent
operations for the exhibition of " Line clear " for
successive trains.
Both systems aim at obtaining changes in the
indications of the instruments without the interven-
tion of the signalmen at either end. Whether this
is desirable is a question upon which opinions may
differ considerably, and opens a wide field for argu-
ment on the functions which should, or should not,
be performed by the signalman. Whether the signal-
man is to be divested of responsibility, and work as
an automaton under the control of the apparatus, or
whether he himself is to be the controller of the
apparatus, with such restrictions against the chance
of error on his part as experience suggests and
•circumstances allow, are points which it is impossible
RAILWAY SIGNALLING. 237
to settle off-hand. It does not, however, appear
desirable to the author to carry the automatic working
to the extent shown by Figs. 79 and 80, in so far as
the clearing of the line on the passing of the train
out of the section. Consider what is meant by the
" Train out of section " signal as given under the
ordinary conditions of working. Clearly it is an.
intimation from one signalman to the other that the
former has satisfied himself that the whole of a train
previously signalled between them has passed out of
the section, and the subsequent indication, " Line
blocked," is a permanent reminder of this. In such
a case both signalmen are concerned in the operations
necessary before the " Train on line " indication is
changed to " Line blocked."
On the other hand, if the signalman at the receiving
end relies upon the indication exhibited in conse-
quence of the passage of the train over the treadle
before giving the " Train out of section " signal, he
may come to rely upon it too implicitly, and, since
the first vehicle actuates the treadle, he may on
occasion find that the line has been cleared by an
incomplete train. It is true that the signalman is not
relieved from responsibility in seeing that the whole
of the train passes, but the treadle operates to exhibit
" Line blocked " whether this is the case or no.
The signalman at the sending end has no means ot
distinguishing the indication exhibited in consequence
of the actuation of the treadle at B, from that due to
failure of the line wire or the batteries operating the
" Train entering section " indication. It is true that
the indication " Line blocked " may be followed by
238 RAILWAY SIGNALLING.
the " Train out of section " signal, but that is not
its proper order.
To the author it appears that the only legitimate
use of automatic apparatus is such as will prevent
the signalman from performing such operations as
indicate changes of condition before the time arrives
for doing so. Anything which tends to lessen the
sense of personal responsibility on the part of the
persons charged with the working of traffic is to
be deprecated. By all means the signalman should
be checked in his actions by the trains he operates,
but these trains should take no part in performing
the operations pertaining to the signalling itself.
Single-Line Working. — The principles under which
single-line block working is carried on differ in no
way from those adopted for ordinary double-line work,
the section limit being imposed upon trains passing
between any two adjoining cabins. Inasmuch, how-
ever, as trains passing in either direction have neces-
sarily to pass over the same line of rails, it is obvious
that some other precaution than that afforded by the
ordinary form of block is necessary to ensure that two
trains shall not, through negligence in any way, enter
the section from opposite ends at the same time. This
is generally accomplished by the " staff," or "staff and
ticket," system of working single lines, to which block
working is often merely supplementary.
In single-line working the line is divided into a
convenient number of parts, at the junctions between
which passing places are provided for trains pro-
ceeding in opposite directions ; and the driver of
any train passing through any such section, as B C
RAILWAY SIGNALLING.
239
•(Fig. 83), must obtain from the signalman at the
entrance to the section some visible authority other
than, and supplementary to, that given by the usual
FIG. 83.— Staff Sections, B-C, C-D.
mechanical outdoor signals, and must deliver the
same to the signalman at the exit end on his arrival
there. In the case of the simpler single lines this
FIG. 84.— Staff and Tickets.
authority to proceed is given by the signalman handing
the train staff (Fig. 84) to the driver of the train about
to enter the section. As there is only one staff to
240 RAILWAY SIGNALLING.
each section, and as no train may enter a section
without the staff accompanying it, the driver, on
receiving the staff, knows that no train will be sent
from the opposite end, and he may therefore proceed
as far as the next staff station. It will be noticed
that the signalmen at intermediate staff stations will
have two staffs to deal with, whilst the signalmen
at the ends of the single line will have only one to
handle. In order to prevent interchange of staffs,
each is, in some way, made distinct from the others,
either by difference in form or colour, or by being
appropriately lettered.
Trains on single lines worked by "staff" alone are
liable to considerable delay, more especially where the
line is fed with traffic at one or more points, such
as at C (Fig. 83). If a train is sent from B to
C, say, and takes the staff, no train can pass
between these points in the same direction until
the staff has been returned to B. This may be
done by a train passing from C to B in the
ordinary course, or a special engine may be sent
with the staff to B ; or, in the event of an engine
not being available, the staff may be sent by a
messenger on foot, or horseback, if the circumstances
are sufficiently urgent. In any case, considerable
delay to traffic results from any deviation from the
ordinary or prearranged working of the line, and
special traffic must be carefully arranged to fit in
with the ordinary, and special advice of additional
trains must be given to the officials concerned in
the working of the line, or that portion affected.
In order that trains may pass over any staff section
RAILWAY SIGNALLING. 24!
in the same direction in succession, the modification
known as the " staff and ticket " is introduced, the
" ticket " being a supplementary authority for the
driver to proceed, which is understood to be available
for use only when the staff for the section to be entered
is in the possession of the signalman at the entrance
to the section.
The staff usually takes the form of a cylinder of
brass or hard wood of distinctive shape, and has
engraved upon its surface the names of the points
constituting the staff section for which it is available.
The "ticket" is usually a flat iron plate of oval or
rectangular form (Fig. 84), and is similarly lettered.
In addition, the very necessary information respecting
the direction in which it is to be used — i.e., for " up "
or " down " journeys — and its number are marked
upon it. By these means the " ticket " affords a
check upon the signalman, and ensures the use of
the proper ticket, and also affords information to the
driver, by its number, of the condition of the line
through which he is to proceed. Each cabin is
provided with a small lock-up box, in which a certain
number of " tickets " are kept for use as required.
The key for this box forms part of the staff, and the
ticket-box, therefore, can only be opened by the
signalman who has possession of the staff. If a
train is to be sent away from the staff station, and
it is certain that another will require to follow it
before the staff could be returned under ordinary
working conditions, a " ticket " is given to the driver,
and the staff is retained by the signalman until such
time as it becomes necessary for the staff to be sent
16
242 RAILWAY SIGNALLING.
to be available for trains in the opposite direction,
tickets, in their proper numerical order, being
delivered to drivers of all successive trains except
the last, to whom the staff is given. This method
constitutes a great advance on simple staff working
and enables traffic to be handled with much greater
facility. Even with this modification, however, the
schedule of arrangements of trains must be closely
adhered to, and if any deviation from it is made, or
trains are sent unexpectedly, it is a mere matter of
chance if delay does not ensue.
Fig. 83 shows a single line divided into staff stations
with passing places for trains proceeding in opposite
directions. The number of staff sections for any line
will depend upon its length, the amount of traffic
passing over it, and the number of points at which
traffic is lifted or delivered. For busy lines it is, of
course, of advantage for the staff sections to be short,
in order to lessen the delay to trains waiting for
others to clear the section. On the other hand,
cutting the line into numerous staff sections involves
expense in providing passing places, staff cabins, and
signalmen ; and delays to through traffic in conse-
quence of the frequent slackening of speed to exchange
staffs or "tickets."
Where the " staff and ticket " system is in use,
and trains proceeding in the same direction may
follow each other, a combination of the block system
with the staff is found to be advantageous. In
Fig. 85 a portion of the staff section, B-C, is shown
as split into three block sections, B-M, M-M1, and
M^C. Block apparatus of any suitable kind is
RAILWAY SIGNALLING. 243
provided in B, M, M1, and C, and the usual com-
plement of mechanical signals is provided at each
place. A train leaving B, say, with a ticket for
C would be signalled on the block instrument in the
usual way, and would be cleared back to B when
it passed M and was proceeding to M1. A second
train might then be sent away from B in the same
direction either with a second ticket, or the staff,
as might be desirable. Between B and C the trains
are worked under block rules only, and they are
not required to stop or slow down for the exchange
• of staffs at M or M1, but may run straight through,
0 S ((
FIG. 85.— Staff Section B-C with Intermediate Block Sections, B-M,
M-M1, M^C.
so long as the proper mechanical signals are exhibited.
At the same time there is nothing to prevent the
ordinary work of lifting or leaving traffic being
performed at either M or M1. In this way, as will
be evident, a glut of traffic passing in one direction
can be much more readily dealt with than by the
simple staff, or staff and ticket, systems alone.
Although the fact that between B and C there may
be three trains would seem a violation of the
principle underlying the staff system, yet, on closer
examination, it will be evident that the primary
object of the staff is to prevent trains entering a
section from opposite ends at or about the same
16*
244 RAILWAY SIGNALLING.
time, and the trains in the case considered are all-
passing in the same direction. Further examination
will show that the staff section space has been
replaced by a shorter block section space, and so
long as no irregularities occur the system is perfectly
safe.
There is nothing special in the instruments used
for single-line block working where nothing more
than the mere indication of the condition of the line
is required. Any form of instrument in use on
double lines may be easily adapted to single lines.
The single-needle instruments described in connection
with double-line working only require to be provided
with a pin at each end for pegging the needle, instead
of at one end only, there being, of course, only one
indicator for each section, and only two wires required.
Winter's block instrument (Fig. 45) simply requires
Z of the line battery to be connected to the terminal,
Sp, to enable it to be used for single lines. In this
case one instrument serves for the two sections which
are controlled from the cabin. Block instruments, in
the design of which some attempt has been made
to secure a degree of automatic control, have some
claim to be considered as capable of being used on
single lines without the aid of the staff system,
but such adaptations have made no progress in
this country. Other instruments, such as Walker's,
Harper's, Fletcher's, and the single-needle instruments,
can only be used to facilitate traffic over the lines,
and are subordinate to the staff as a safety appliance.
The want of flexibility in the staff system, and the.
delay consequent upon any deviation from the ordinary
RAILWAY SIGNALLING.
245
or prearranged working, has led to modifications, and
instruments have been devised by means of which
safetyjis ensured, and much of the delay to the traffic
is obviated. The principal alteration consists in the
Staff Lock A
Local Battery
FIG. 86. — Webb and Thompson's Electrical Train Staff Instrument.
abolition of the single staff governing the passage of
traffic in both directions, and the substitution of a
number of staffs at each end of the section. The
.staffs for any one section are all similar, and are of
246
RAILWAY SIGNALLING.
equal value ; and these are contained in instruments,,
placed in the cabins, which are so constructed that
only one staff can be withdrawn from the instrument
for any section at a time. Whilst such an arrange-
ment enables traffic to be more readily handled, and
releases the rigidity of the simpler system, it is obvious
that the precautions to be observed in such a method
are necessarily more elaborate, and the control of the
instruments containing the staffs must be absolute.
An interesting instrument, from an electrical point
of view, for this purpose, is Webb and Thompson's
electrical train staff instrument, which is shown by
Figs. 86-88.
Fig. 86 shows front and side views of the exterior
of the instrument with a number of staffs in position,,
together with the two switches, indicator, and bell.
RAILWAY SIGNALLING. 247
key. Staffs can only be inserted or withdrawn from
the instrument at the opening, H. Staffs may be
inserted at any time, but can only be withdrawn under
prearranged conditions.
Fig. 87 represents the arrangement by which the
staffs are locked in the staff pillar. The cam-wheel,
C, turns on its centre. When a staff is raised with
the object of withdrawing it, it must lift the bent
lever, /, before entering the passage to H. The com-
pound electromagnet, M, is lifted by the movement
of /, and if it is energised properly it lifts the lock, L,
with it. Otherwise L remains in the position shown.
If L is raised with M, the motion of the staff, under
the movements of the signalman, towards H causes
the cam-wheel, C, to turn, and allows the staff to
pass to H, and be withdrawn there. In the event
of M not being properly energised, L will remain as
shown, and the cam-wheel being locked against
turning in the necessary direction, it will be impossible
to withdraw the staff under the conditions. Obviously,
therefore, the withdrawal of a staff depends upon the
excitation of the magnet, M, whilst a glance at Fig. 87
will show that staffs may be put into the pillar at any
time.
The instrument is provided with a switchboard
(Fig. 88) of five switches, four of which are two-way
switches, whilst the fifth has only one contact. The
switches marked No. i and No. 2 are actuated by
the movement of the cam-wheel (C, Fig. 87), and
change the positions of contact every quarter revolu-
tion of C.
The switch marked " bell key " is actuated by the
248
RAILWAY SIGNALLING.
depression of the lever similarly lettered in Fig. 86.
Normally the bell key (Fig. 88) makes contact at
"23"; when the lever is depressed, contact is made
at " 33." The " local battery key " and " staff lock
FlG. 88. — Webb and Thompson's Electrical Train Staff Diagram ot
Connections for One Section of Single Line.
switch " bars (Fig. 88) are operated by the switch on
the right hand of Fig. 86. When the handle is as
shown by Fig. 86, the " staff lock " bar makes
contact at "22" and the "local battery" bar is
RAILWAY SIGNALLING. 249
disconnected. When the handle is placed to " For
staff " the " staff lock " bar makes contact at " 32 "
and the "local battery" bar at 31. The cut-off
switch (Fig. 88) is operated by the left-hand switch,
shown in Fig. 86. When the indicator attached
to the handle is in the position shown it does
not affect the "cut off" switch, shown in Fig. 88,
but when held hard down in the position shown the
spring is displaced from the upper stud, and the
circuit broken. The indications " Staff in," " Up
staff out," " Down staff out," of the left-hand switch
do not depend in any way upon the actual conditions
being similar to the indication exhibited. They are
merely reminders which the signalman may or may
not place in accordance with the actual state of affairs,
without affecting the working of the apparatus. The
staff lock electromagnet, M (Fig. 87), is shown
diagrammatically in Fig. 88, and the construction of
the indicating magnetic needle is shown in the same
figure.
All train distinguishing and other signals passing
between the signalmen at opposite ends of the staff
section, are given by a bell code ; the bell being
rung by depressing the key shown on the front of
instrument in Fig. 86.
Bell Code. — The bell code in use does not differ
materially from that in use for double-line working in
cases where all distinguishing signals are by bell, and
need not be further referred to.
The operation of withdrawing a staff at either
cabin is very simple, and can only be done by the
joint action of the two signalmen at opposite ends of
250 RAILWAY SIGNALLING.
the section. (The connections being identical at eacb
each end only one station is shown in the diagram.)
Assuming that a staff is to be withdrawn at " A "
under the conditions of the apparatus as shown by
Fig. 88, and that the preliminary notification signals
have been given and accepted, the operation is as
follows : " A " places the right-hand switch to " for
staff," " B " depresses bell key and keeps it down,
" A " withdraws staff, and then turns the left-hand
switch to "up staff out," turning the switch hard
down before releasing it. This latter action notifies
" B " that the staff is out, and he releases the bell
key. This completes the operation, the right-hand
switch at "A" being replaced automatically to
" for bell " during the operation of withdrawing the
staff.
Remembering that the " local battery " bar is
making contact at " 31," and the " staff lock " bar
at "32," at "A," and that the "bell key" at "B"
is making contact at " 33," it will be seen that two
currents are passing around the staff lock electro-
magnet, M, at " A " ; and following the directions of
the currents through the windings of the "local"
and " line " coils respectively, it will be found that
the resultant magnetic effect is to produce poles at
" N " and " S " (Fig. 88). Under these circumstances
the lock, L, will be raised, with the electromagnet, M,.
by the movement of the lever, I, when the staff is being
withdrawn from the pillar towards H (Figs. 86 and 87).
The paths of these currents, in the positions occupied
by the automatic switches Nos. i and 2, at " A " and
" B," is as follows.
RAILWAY SIGNALLING.
251
"A."
" B."
From carbon of line
battery to 12, 33, 28, 5,
cut-off switch and galvano-
meter, 6, 18, 25, 26, 17,
14, 9, and line wire to
10, 15, 16, 27, 24, 19, ii to
zinc of line battery.
9, 14, 17, 26, 25, 18, 6,
cut-off switch and galvano-
meter, 5, 28, 23, 20, 29, 32,
2, line coils, i, n, 19, 24,
27, 16, 15, 10 to earth and
Local battery.
From carbon to 8, 31,
30, 4, local coils, 3, 7, to
zinc.
These currents excite the electromagnet, M, and it
will be noted that not only are two currents necessary ,.
but their directions must be in accordance in order to
do this. Since the electromagnet is provided with a
complete magnetic circuit, either of the two currents
would fail to excite it, effectively, for the purpose it is
intended for alone ; and if the direction of either
current is reversed, the effect upon the lock pawl, L,
will be nil. The method of obviating the disadvan-
tages of an air-gap by making the lock pawl, L, the
armature for the consequent poles developed is also
worthy of notice.
The movement of the cam-wheel changes the points
of contact of the switch bars Nos. i and 2 from "24 "
and "25" to "34" and "35." The breaking of"
252 RAILWAY SIGNALLING.
the contacts of these bars with "24" and " 25 "
"breaks the path of the current from " B," and releases
L, from M ; this path being immediately replaced by
another through " 34 " and " 35." If the new path
is traced it will be found that the current from B has
been reversed in direction through the line coils at
'" A," and consequently poles are not formed at " N "
and "S" as before, and the lock pawl will be
unaffected by any subsequent movement of M whilst
these conditions obtain. Not only is this the case,
^ut if the operations described are gone through with
the object of liberating a staff at " B " it will be
found that the direction of the currents through the
line coils at " B " is such as, in conjunction with the
fixed direction of the current through the local coils,
is ineffective for the purpose of raising L in order to
allow the cam-wheel to turn.
The instruments are said to be " out of phase "
-when the switch bars Nos. i and 2 make different
contacts at the two ends of the section, and they can
only be made operative again by putting them " in
phase." This may be done by replacing the staff in
either A's or B's pillar. In the first case the switch
bars Nos. i and 2 at "A " return to the top contacts
'" 24 " and " 25 " ; in the second case the switch bars
at " B " are caused to make contact with the bottom
springs " 34 " and " 35," and thus make contact at
the same points as the similar bars do at " A."
Shortly, if the paths of the currents are traced, under
the various conditions necessary, it will be found that
.staffs may be withdrawn at either place when the
switch bars Nos. i and 2 make similar contacts only.
RAILWAY SIGNALLING. 253,
It will be noticed from the path of the line current
that it passes through the galvanometer at each,
cabin, and, therefore, during the time the bell key
at " B " is depressed, to enable a staff to be with-
drawn at "A," the galvanometer needles are deflected.
Some means of notifying " B " of the completion
of the operation of withdrawal is necessary, and
this is effected by breaking the circuit at the cut-off
switch by pressing it hard over, as already observed.
Both galvanometer needles assume a vertical position,
and the signalman at " B " accepts this as an indi-
cation of the completion of the operation.
The right-hand switch is automatically replaced
to " for bell " by the turning of the cam- wheel, and
a study of the connections will show that at the
moment of replacement the current will pass through
the bell at "A." No notice of the one blow on the
bell, resulting from the change of connection, is
taken, and it is of no significance whatever, since
the man engaged in withdrawing the staff requires
no signal to tell him when he has got it out.
Such an instrument as that just described is.
obviously a great advance on the simple single staff
and ticket system, in so far as facilitating the working
of traffic and immunity from danger of accident is
concerned. Under ordinary circumstances there need
be no delay, as in the single-staff system, owing to
the staff being away; and the lock, L, being con-
tained in a strong lock-up iron case, if the batteries
and connecting wires are protected against being
tampered with it is not possible to, even burglariously,,
take a second staff out of either pillar. This, ot.
254 RAILWAY SIGNALLING.
course, is the premier object of the design, without
which it would be worthless as an instrument for
single lines. A minor point in connection with the
design of the instrument may be noticed. It is
that, although both men are actively engaged during
the whole time occupied in withdrawing a staff at
either end of the section, only one of them is
concerned with its replacement. Under these cir-
cumstances it will be observed that it is not essential
for the signalman at the sending end of the staff
section to remain in his cabin until the last train
through the section at night, say, has been signalled
FIG. 89.
out. The staff can be placed in the pillar at the
opposite end, and the two instruments put in " phase,"
without the assistance of the man at the point from
which the train started. An understanding between
the signalmen would, of course, have to exist before
this could be done.
Single lines differ considerably in character. Some,
as Fig. 89, end as single lines ; others, again, form a
connecting link between two double lines, as Fig. go,
and feed both ; with such a line as* Fig. 89 the traffic
is bound to balance — i.e., the same number of trains
RAILWAY SIGNALLING. 255
must emerge at the junction as enter it — and the
number of staffs kept at each staff cabin will remain
fairly constant. In such a case as is shown by Fig. 90
this may not occur, especially where the single line is
fed from a number of points in its length, and there
exists a number of staff stations between the extreme
points of the single line. A number of trains may
enter at one junction and leave by the other, and
there would thus be an accumulation of staffs at some
point and a corresponding denudation at another
point, dependent upon the preponderating direction
FIG. 90.
•of traffic. In such cases, for instruments such as
Webb and Thompson's, and others of similar design,
special means have to be taken to restore the balance
of staffs, or the line would ultimately be in the same
condition as with a single-staff system. This is
usually done by giving to the telegraph lineman for
the district, a key which will open the case of the
instrument and enable him to lift the lock, L, by hand,
until a sufficient number of staffs has been removed
from the pillar having a surplus, for conveyance to the
point where a deficiency exists. Of course, this is
256 RAILWAY SIGNALLING.
only done under the supervision of the more respon-
sible officials of the locality ; and the person removing
staffs in this way must give and take receipts for them,
and it must only be done at such time as no staff is
in ordinary use. In this connection it will be noticed
that an even number of staffs must be removed for
conveyance to the opposite end of the section, in
order that the instruments may be left in " phase "
for ordinary work during the time occupied in con-
veying the staffs from one point to the other. If the
lineman conveys his bundle of staffs by a train passing
in that direction, the driver must be furnished with a
separate one, in order to leave the instruments out of
" phase " during the passage of the train through the
section.
On single lines where the traffic is light at night
provision is made for switching out an intermediate
staff station, staff working being carried on between
the two cabins on each side. In such cases the
instruments for working the longer section are distinct
from those working to the intermediate station, and
the staffs are of such form and size as to prevent them
from being worked in conjunction with any instrument
but the right one. The switching operation is some-
what elaborate, and a good idea will be more readily
formed from the instructions given for its performance :
" As soon as the train next before the time specified
in the working time-table for switching out has passed
B and has arrived at C or A, as the case may be, and
train out of section has been received for it at
B, the signalman at B must ascertain by single needle
or telephone, as the case may be, that all the staves
RAILWAY SIGNALLING. 257
at A and C are in their respective staff pillars.
Having ascertained that such is the case he must
give ('closing cabin signal') on bell , which
signal must be acknowledged. B must then peg
down the bell key of each of his staff instruments
by means of the pin provided for the purpose, and
A and C must each of them hold down the bell key
of the instrument working to B, which will be shown
at B by the deflection of the needles. This action
electrically unlocks the switch at B and permits that
station to switch out, which he must do by depressing
the lever on his switch instrument and turning the
pointer from ' Switched in ' to ' Switched out.'
Having done this, he must send to A and C on the
single needle, A A A which signal must be
repeated to show that it has been understood, which
will call the attention of these stations to the fact
that the action of closing B has been accomplished
(or where single needles do not exist the communica-
tion must be made on the telephone). On the receipt
of this signal on the single needle, or the notification
by telephone, A and C may cease to hold down their
keys. All the instruments at the three stations have
thus become disconnected, and the staves, both local
and through, locked up in them. In order to bring
the through staff instruments into operation, A and C
must then turn the pointer of their battery switches
from intermediate station to through section, which
act will connect the through instrument at A with
the through instrument at C. Stations A and C
must then exchange the test signal with each other,
and having done so must intimate to B that their
17
258 RAILWAY SIGNALLING.
through instruments are in circuit by sending him,
by the single needle or telephone, the word 'through.5
B is thus made aware that A and C are working on
the through circuit, and after switching out his
cabin-to-cabin single needle or telephone in the usual
manner, if he is supplied with one, and unpegging
the bell key on each of his staff instruments, he may
close has cabin and leave."
" The rules for opening B are as follows : On the
arrival of the signalman at B he must first switch
in the cabin-to-cabin single-needle instruments if
they exist (but if the telephone is in use without a
single needle then a verbal communication must be
made on that circuit), and then send fifteen beats
on the needle, thus (five to the left, five to the right,
and five to the left) to A and C. If there is no staff
out of the pillars, A and C must each return the
code of fifteen beats, and then hold down their bell
keys on the through staff instruments, which will
unlock the switch at B. B must then depress the
lever of his switch instrument and turn the pointer
from ' Switched out ' to ' Switched in,' and having
done so he must move the handle of the single-needle
cabin-to-cabin instrument to and fro three times —
thus, N, N, N — which will call the attention of those
stations to the fact that the action of opening B has
been accomplished, and those stations must turn
the pointer of their battery switches to intermediate
station. A and C must then each of them exchange
with B the test signal on the bell, and working by
local staff can then be commenced."
Arrangement of Circuits. — Fig. 91 represents-
RAILWAY SIGNALLING.
259
diagrammatically the arrangement of circuits where
switching from "intermediate5* to "through" sections
is in operation. As will be seen, an additional line
260 RAILWAY SIGNALLING.
wire is provided for the " through " section instru-
ments at A and C, and switches are provided at these
places by which the batteries may be used for either
the " intermediate " or " through " instruments. The
main switch by which the change over is effected
is situated at B. It consists of two distinct sets of
switches of four each ; one set being operated by
depressing the tapper key, the other set being operated
by the arrow-shaped handle. The four switches shown
in connection with the key are in their normal position,
and change of position of the contact points can only
be maintained by keeping the key depressed. The
four switches on the left will maintain upper and
lower contacts according to the position of the handle
by which they are operated. The operation of the
left-hand contacts from top to bottom, or vice versa,
is controlled by locks which are released by the
action of two electromagnets of similar construction
to that used in connection with the staff lock and
shown in Figs. 87 and 88. When the bell keys of
the intermediate instruments at A and C are held
down, and the similar keys of the two instruments
at B are pegged down, depression of the tapper key
on the switch causes currents to pass, from A and B,
through the coils of one electromagnet, and currents
from B and C through the coils of the other. If
these currents are in "phase" with each other the
electromagnets are energised, but not otherwise, and
the handle of the left-hand set of switches may be
turned. Assuming that the left-hand switches occu-
pied the positions shown by Fig. 91 before the
operation commenced, the movements indicated will,
RAILWAY SIGNALLING. 26l
if traced, be found to have disconnected the line wires
of the " intermediate " instruments, situated at A,
B, and C, at B's switch, and to have joined the
" through " section line wire through at the same
place. By altering the positions of the battery
switches at A and C, the batteries previously used
for the " intermediate " instruments are connected
to the " through " instruments. Further considera-
tion of the connections will show that the switches
on the right of the change-over switch are simply
used for the purpose of directing the currents set
up by the depression of the keys of the instruments
at A, B, and C, through the releasing electromagnet
coils, and their use is temporary only. The actual
change of connections is made by the left-hand
switches. Further consideration of the diagram will
show that the movement of the left-hand switches
breaks the circuits from A, B, and C, through the
lock coils and releases the locks and thus prevents
the left-hand switch handle from being replaced in
the position from which it has just been moved
without the whole operation being repeated on the
other instruments.
The operations just described constitute the change
from " day " to " night " or " intermediate " to
"through" instruments. The reversal from "through"
to " intermediate " is similarly made, but as B has
no instruments on the " through " circuit the pegging
of the instruments at B is not a feature of this
operation. Consideration of the conditions obtaining
in switching from "through" to "intermediate"
will show that only one of the releasing electro-
262 RAILWAY SIGNALLING.
magnets (the lowest in Fig. 91) will be in use for
this operation, the currents from A and C passing
through different coils of the same electromagnet
which operates on the one lock in this position.
Consideration of the system as a whole will show
how absolute the control of the staffs and the
switching out of intermediate stations actually is. In
all cases of switching the three men at A, B, and C
are all actively engaged, and the operation cannot be
performed by any two of them alone. Not only is
this the case, but owing to the fact that the switching
currents must be in "phase" the possibility of error
from attempting to switch when a staff is out of any
one of the six pillars is prevented. Indeed, so highly
is the system approved by Board of Trade officials
that they allow fixed mechanical signals to be dis-
pensed with at stations, situated between the staff
stations, at which trains are required to stop.
Another feature connected with the switching out of
intermediate stations during the times when traffic is
known to be slack, other than the saving of wages,
etc., is the possibility of using one set of instruments
when, from any such cause as a line fault, the set in
use has failed. This is an advantage which is not to
be despised where traffic is heavy.
Consideration of the instructions issued for switch-
ing show clearly that the instruments must be supple-
mented by some other means of communication in
order that the various stages of the operation may be
arranged and its completion reported. Where such
means of communication do not exist it must of course
be provided, and constitutes an additional expense,
RAILWAY SIGNALLING.
263
but there are few places now which are not provided
either with a telegraph instrument or a telephone, and
there will be less in the future.
Tyer's Tablet Instrument. — Another form of
instrument in extensive use for single line work is
Tyer's tablet instrument, three varieties of which are
shown by Figs. 92-95. The electrical connections for
FIG. 92.
-the respective instruments are shown by the diagrams
Figs. 92A, 93A, and 95A.
The " tablet," which constitutes the authority to
proceed through the section, is usually an annulus of
metal appropriately numbered and lettered in accord-
ance with the section it is intended to represent. The
264
RAILWAY SIGNALLING,
EJS.
FIG. 92A.
tablets are placed in suitable receptacles in the body
of the instrument, and the arrangement of the
mechanism is such that only one tablet can be out
RAILWAY SIGNALLING. 265
at one time, and this removal can only be made after
certain conditions have been complied with.
In the instrument shown by Figs. 92 and Q2A the
tablets are inserted in radial slots cut in a rotating
disc, the motion of which is controlled by a pawl
and ratchet wheel, the pawl in turn being operated
by the locking electromagnet. The rotation of the
tablet disc is effected by turning the knob, K, and
movement of the disc actuates the commutator, Q,
shown in Fig. g2A. The instrument is also provided
with an indicator, I, a bell plunger, a switch plunger,
a bell, a relay, and a small out-off switch shown at
the bottom of the diagram. Tablets are inserted or
withdrawn at the opening covered by the cap, C
(Fig. 92). The operation of withdrawing a staff, at
A say, is carried out as follows, after the usual bell
signals have been exchanged. A grasps the knob, K,.
and turns it as far as possible from left to right,
and depresses the switch plunger, S. At the same
time B depresses his bell plunger. Under these com-
bined operations A's instrument is unlocked, and by
turning the knob, K, from right to left he is able to
bring a tablet into position under the cap, C. It is
then only necessary to raise the latter in order to
remove the tablet. The lifting of the cap, C, mechani-
cally locks the rotating disc, so that only one tablet
can be removed at a time, and this lock is only
removed by placing C in its original position, when,,
of course, the instrument is again locked by the pawl
and ratchet wheel.
Consideration of the diagram of connections will
show that the depression of S, at A, during the opera-
266 RAILWAY SIGNALLING.
tion of unlocking the instrument at that place, simply
provides a path for the local current set in action
by the upper tongue of the relay making the proper
contact for the completion of the local current through
the locking magnet, L. As shown in Fig. 92, the
proper point of contact is on the left relay. The
current from the distant station, B, due to the
depression of the bell plunger at that place, simply
passes through the indicator and relay, but the
actuation of the latter for the purpose of unlocking L,
in conjunction with the simultaneous depression of S,
depends upon the direction of the current sent from
B. The direction of this current is controlled by the
commutator, Q, and a glance at Fig. Q2A will show
that the release of either instrument depends upon
*the commutator occupying similar positions at both
places.
Provision is made for disconnecting the local battery
whenever a tablet is immediately under the cap, C.
This is done by the tablet, when in position in the
rotating disc, depressing the cut-off switch shown at
the bottom of Fig. Q2A. No signals can be sent
under these circumstances, and for this reason it is
necessary to turn the knob, K, from left to right after
a tablet has been inserted before the clearing line or
arrival signal can be sent to the rear station.
With this form of tablet instrument a tablet may
Tbe returned to the instrument from which it was
taken, and a tablet may therefore be withdrawn for
local shunting purposes, involving use of part of the
staff section only, without the necessity existing of
•conveying it to the opposite end of the section. One
RAILWAY SIGNALLING.
267
feature of this form of the tablet instrument is the
absence of any indication of the condition of the line.
Figs. 93, 94, and 93A show another form of the
tablet instrument. In this form tablets are inserted
.by raising the cap, C (Figs. 93 and 94), and with-
FIG. 93.
drawn by pulling out the slide, S, at the bottom
of the instrument. The tablets are contained in a
hollow column above the slide, the lowest tablet
fitting into a recess in the slide, and having its
upper surface flush with that of the slide. A number
of auxiliary slides, s, are provided to assist in support-
268
RAILWAY SIGNALLING.
ing the tablets, which are lowered into the bottom
slide as necessity arises. The positions of the tablets
FIG. 93A.
are visible from the front of the instrument, so that
the approximate number available for use at any time
may be observable, in order that any transference of
UNIVERSITY
RAILWAY
tablets, rendered necessary by unbalanced traffic, may
be made in time to prevent delay. The bottom slide
cannot be withdrawn from the instrument unless it
contains a tablet.
The means used for preventing a tablet for one
section being put into the instrument for another
••; •*
FIG. 94.
section are shown in Fig. 94, in which the cap, C,
is shown raised for the insertion of a tablet. A radial
slot is cut in the tablet, which, when the latter is
put in the receiver, fits into a projection for it, and
necessitates the tablet being placed in one particular
270 RAILWAY SIGNALLING.
position when in the receiver. In addition to the
slot, a small hole is formed in the tablet into which
the pin, p, shown on the cap, projects. This pin
must pass through the hole in the tablet before the
cap can be placed down, which must be done before
the lower plate on which the tablet rests can be
released. By forming the hole in the tablet at
different points relatively to the slot, and fixing the
pin, p, on the cap in positions to suit, any tablet
other than one intended for that instrument will
prevent the cap from being placed in the position
necessary to release the lower plate or receiver.
When the cap is in its position for releasing the
receiver the weight of the tablet depresses the lower
plate, and the tablet falls off it and falls into the
column shown by the dotted lines in Fig. 94. The
locking shown between the cap, C, and the receiver
plate is diagrammatic only.
The electrical part of the instrument is shown by
the diagram Fig. g3A. It consists of a two-part
commutator, bell plunger, relay, indicator, bell (which
also acts as a relay), unlocking plunger, electro-
magnetic commutator lock, slide-releasing magnets.
The operation of releasing a tablet is very similar
to that described in connection with the instrument
shown by Fig. 92. The switch, O, is depressed at
the station at which the tablet is required, and the
bell plunger is depressed at the distant station. The
current from the distant station simply actuates the
relay and indicator, and the former, in conjunction
with the unlocking switch, provides a path for a
local current through one or other of the releasing
RAILWAY SIGNALLING. 271
coils. A second local current is set up by the plunger
attached to the bell armature, which passes through
the electromagnet controlling the commutator. The
withdrawal of the slide breaks the two spring contacts
at B, and these remain broken during the whole time
the slide is out. One of these contacts breaks the
circuit through the commutator electromagnet, Mlv
and the other contact breaks the battery circuit to
the commutator and the bell plunger. An auxiliary
circuit, however, is provided at D for the latter, and
is closed by the armature of the releasing electro-
magnets. The lower indication "in" "out" is
actuated mechanically by the turning of the com-
mutator at that place ; the upper indication is
operated by the current, sent from the distant station,
through the relay, after the commutator has been
turned from its normal position.
The construction of this instrument is such as to
prevent a tablet being returned to the instrument
from which it has been taken. The tablet must be
taken to the opposite end of the section. It cannot,
therefore, be used for local purposes only.
The latest form of the tablet instrument is shown
by Fig. 95, and the electrical connections, in diagram,
by Fig. 95A. In this form the electrical portion is
confined to the unlocking of the commutator. Tablets
are inserted and withdrawn by means of the slide
shown at the bottom of the instrument. The operation
of unlocking the instrument is performed by the distant
station depressing the bell plunger for a specified time,
during which the commutator is turned. A considera-
tion of the diagram will show that, as in the other
272
RAILWAY SIGNALLING.
instruments described, the action of the current from
the distant station is confined to the operation of the
relay, and that the actions resulting in the release of
the apparatus are due to the local current. It will,
FIG. 95.
however, be noted that this instrument differs from
the others in that the signalman at the station which
requires a staff is not called upon to contribute in any
way towards the completion of the path of the local
RAILWAY SIGNALLING.
273
releasing current. At the same time he is actively
engaged in the operation at the same time as the
signalman at the distant station, since he must
-complete his portion of the work during the time the
bell plunger is being depressed at the distant station.
It is of considerable importance in tracing the action
of these instruments that the movements required
to release or insert staffs and their order be clearly
understood. For this reason the following extracts
18
274 RAILWAY SIGNALLING.
describing the movements in their proper order are
taken from official instructions :
" If a train or engine is at station A, and requires to
proceed to station B, the signalman at A must give
the proper ' Is line clear ' signal to B, the signalman
at B having ascertained that the line is clear for the
train to run upon, must repeat the signal; if not
prepared to accept the train he must give one beat of
the bell or gong. The signalman at A, after receiving
the proper acknowledgment for accepting the train,
must then give five rings: thus, 4 — i, signifying
' Release tablet.' B must, provided the previous train
has passed his box and there is no obstruction on the
line upon which the approaching train is to run, repeat
the signal back to A. The signalman at A must, if
the old pattern of instrument is in use, press down the
bell plunger and keep it down till the galvanometer
needle rises to its normal position, which shows that
the signalman at B is turning his lower disc ; the
signalman at A must then immediately release the bell
plunger and press down the switch plunger, and keep
it down till the upper disc is turned red, showing the
word 'out,' then release the switch plunger, lift up
the check, draw out the tablet slide, give one beat
of the bell or gong, then give tablet to driver. The
signalman at B must, after receiving the tablet from
the driver, deposit it in the instrument, lettered side
downwards ; then give the ' Train arrived ' signal to A
and immediately turn the lower disc to white, showing
the word ' in ' ; then press down bell plunger, holding
same down for three seconds. The signalman at A
must, after receiving the l Train arrived ' signal from
RAILWAY SIGNALLING. 275
B, press down the switch plunger, holding down the
same till the upper disc is turned to white showing the
word ' in.' Both instruments will then be in their
normal condition.'' The instrument referred to in the
above extract is shown by Figs. 93, 93A, and 94.
" If the new-pattern instruments are in use, the
signalman at B, if prepared to accept the train, must,
after acknowledging the signal, press down the bell
plunger for three seconds ; if not prepared to accept
the train, he must give one beat of bell or gong.
The signalman at A, after receiving the proper
acknowledgment for accepting the train, must turn
his lower disc commutator from right to left, showing
the word ' out,' then draw out the tablet slide,
give one beat of the bell or gong, then give the
tablet to the driver. The signalman at B must,
after receiving the train tablet from the driver, with-
draw his tablet slide empty, insert the tablet, lettered
side downwards, push the slide home, raise and lower
the switch lever on left-hand side of the instrument,
then give acknowledgment of arrival signal. This
will have the effect of reversing the upper disc at
B from 'out' to * in.' B will give one beat in reply,
which will have the effect of reversing the lower disc
at A. Both instruments will then be in their normal
position." The instrument referred to in this extract
is shown by Figs. 95 and 95A.
Consideration of the design of these instruments
will show that the objects aimed at are precisely the
same as those aimed at in the construction of the
train staff instruments already described, although
the means by which these objects are attained are,
18*
276 RAILWAY SIGNALLING.
of course, entirely different in the two forms
instrument. The ultimate object is, of course, the
conversion of the line between any two stations
forming a section into an up or a down line as
necessity requires and circumstances allow. Both
forms of instrument are, in so far as their applica-
tion is concerned, simply developments of the simpler
single staff system which they have replaced, and
rely for their advantages over the original system on
the greater number of the symbols of authority to
proceed which their design enables them to control
effectively. No deviation from the fundamental
principle of the original system is made ; the only
difference is that the authority to proceed through
the section is available at either end as circumstances
require. This, of course, is often a matter of great
importance in reducing the delay to traffic to a
minimum, but the rigid adherence to the original
principle of staff working makes instruments such as
the train staff or tablet unsuitable for working in
conjunction with intermediate block sections, which,
as has already been remarked, is of considerable use
for facilitating the passage of traffic in one direction,
where the single staff and ticket system is in use.
With such systems as those described, block working
as a safety device is unnecessary, owing to the
absolute control established by the instruments over
the staff or tablet used ; indeed, such instruments
themselves constitute a form of absolute block in
that they rigidly impose a space limit between trains
passing through the section they protect. At the
same time the staff section constitutes the minimum
RAILWAY SIGNALLING. 277
length of block section, and the length of these
determines the facility with which traffic can be
handled under certain conditions.
It is questionable whether the rigid adherence to
the principle of the simple staff shown by the design
of the instruments described is really so necessary as
it would appear to be. It will be noted that the
line is converted into an up or a down section, as
the case may be, at the moment the staff, tablet, or
other recognised authority to proceed, is withdrawn
from the instrument. Further, the design of the
majority of the instruments is such that it is not
necessary for the symbol to be conveyed to the
opposite end of the section in order that the line
may be made neutral, as is shown by the arrange-
ments for supplying staffs or tablets for local shunting
purposes, such staffs or tablets being returned to the
instruments from which they were taken. The
handing of the symbol to the driver for conveyance to
the other end of the staff section is a relic of the require-
ments imposed by the original single staff system, in
which the staff was absolutely necessary to the con-
version of the line from a neutral state to an up or
a down section, as the case may be. With such
instruments as those under consideration the convey-
ance of the symbol and its insertion in the other
instrument is only necessary in consequence of their
designs being modelled upon the requirements of
the original staff system, and is really a serious
disadvantage in that it leads, where the traffic does
not balance, to the necessity for special transference
of symbols from one point to another in order to
278 RAILWAY SIGNALLING.
allow of continuous working. In so far as possession
of the staff or tablet constitutes the driver's authority
to proceed, the use of the " ticket" in the single staff
system shows that any subsidiary authority will suffice
for bis purpose so long as it is recognised. This is,
of course, leaving out of consideration the fact that
entrance to the section is controlled by the fixed
mechanical signals in addition to the staff or its
equivalent.
Further consideration on the lines indicated would
show that, with proper precautions, a " staff and
ticket " system, with one staff only at each end, in
which the staff would never leave the station at
which it is placed, and would be used only as a
means to liberate a subsidiary authority of a similar
nature to the ordinary " ticket," would appear to
have many advantages. With such a system the
line could be converted into " up " or " down " at
will, and ordinary block working could be carried on
in conjunction in order to facilitate the passage of a
number of trains in the same direction, the number
of trains proceeding in the same direction in any
one staff section being determined by the number of
intermediate block sections, these latter being in
accordance with experience of the traffic on the line.
Such a system as here outlined would not be difficult
to devise, and would involve nothing extraordinary in
the way of apparatus, whilst it would appear to meet
all the requirements of single lines.
Permissive Block Working. — In certain cases
absolute block working is not necessary in conse-
quence of the character of the traffic dealt with, and
RAILWAY SIGNALLING. 279
•is undesirable on account of its volume and the
necessity for dealing with it in comparatively large
batches. Such cases have to be dealt with in a
different way. In many cases block working is
dispensed with altogether, and the various trains
signalled by bell only. In other instances a modified
form of signalling, known generally as the permissive
block, is made use of. Practically speaking, it is not
entitled to the name, since no attempt is made to
preserve the space limit between successive trains,
which is the essential feature of the absolute block
system. Probably two or three instances of actual use
of this system, with the advantages obtained, will do
more towards showing the necessity for, and the
benefit accruing from, this method of working than
anything else.
Three examples of lines on which permissive block
working is in use are shown by Figs. 96, 98, 100. In
Fig. 96, the passenger station, H,is the virtual junction
for trains from T, P B, Y, W, and L. Trains arriving
at H from P, Y, P B, and W proceed no further, and
passengers travelling by these trains, en route for T or
L, are transferred to other trains at H. It frequently
occurs that a train from T is at the up platform when
trains from P, Y, and P B which require to connect
with it arrive. Hence these trains must pull up at the
same platform, in order that passengers who desire to
change for L may do so, the bays being too short and
not sufficiently numerous to accommodate the later
trains. Similarly, trains from W arrive on the down
line with passengers to connect with a train already at
the platform ready to proceed to T, Y, P, or P B.
280
RAILWAY SIGNALLING,
RAILWAY SIGNALLING.
28l
Hence block signalling, as commonly understood,
cannot be carried on between A and B (Fig. 96).
If bell signals only are used in such a section r
considerable responsibility rests upon the signalmen,
and great care has to be exercised in order to ensure
that trains shall not enter the section from either end
at too high a speed in the event of the line being
already occupied. Under such circumstances the
signalmen have no reminder of the condition of the
FIG. 97.
lines other than that afforded by the bookings in their
train-books, and the danger of sending trains into the
section is further enhanced if a curve exists on the
line, or fog prevents the whole of the section being
visible to the men at each end.
The instrument shown by Fig. 97 is used as an.
indicator of the state of the lines in the section A B
at H. It is simply an ordinary S N block instrument,
such as is used for absolute block working in other
282 RAILWAY SIGNALLING.
places, but differs in the lettering of the dial, and in
provision being made to peg the handle in a vertical
position as shown, in addition to the two ordinary
positions on either side of the vertical. The dial is
lettered on the upper left-hand quadrant " Line occu-
pied," and on the upper right-hand quadrant " Line
clear." The lower half is lettered "Line blocked."
Signals are given between A and B by means of
separate bell communication in exactly the same
manner as for absolute block working. If A transmits
the " Is line clear " or " Be ready " signal to B on
the bell, the response of the latter will depend upon
the actual condition of the line. If the line is clear
of trains, B will reply as per code, and peg the needles
to " Line clear." If the line is already occupied, B
replies to the bell signal as before, but pegs the needle
••to " Line occupied." These are the preliminary
signals, corresponding to the " Line clear " signal in
absolute block working, which are given on the
approach of a train to A, and upon the answer given
by B to this signal depends the action taken by A in
tforwarding the train into the section. If the needles
are pegged to " Line clear," the signalman at A will
lower the home signal, and allow the train to pass in
the usual way. If the needles are pegged to " Line
occupied," the train must be sent forward at caution,
the home signal being kept at danger, and the train
being brought forward by hand or other special signals.
On the train entering the section A B, the usual
•" Train on line " signal is sent by A, and B, in
response, unpegs the needles from "Line clear" or
** Line occupied," as the case may be, and pegs the
RAILWAY SIGNALLING. 283
handle of his instrument in its vertical position, when,
the needles at B and A being vertical also, the
indication exhibited at both cabins is " Line blocked."
As successive trains pass out of the section the
" Train out of section " signal is given for each, as in
the absolute system, the handle being pegged in the
vertical position at the receiving end afterwards for all
trains except the last one of any group of trains.
When the last of any group leaves the section,
it being then clear, the handle is unpegged, but the
indication shown by the needles is unchanged and
remains at " Line blocked." The difference of the
indications, section clear of trains, and section
occupied, at the receiving end of the section, consists
in the position of the peg for the handle, except
during the time " Line occupied " or " Line clear "
is being exhibited. In the first case the peg is
inserted, as shown by Fig. 97 ; in the second case
it hangs in front of the instrument by the chain to
which it is attached. The right and left indications
of the needle simply show that permission has been
given for a train to enter the section ; in the first
case it may run straight in without stopping ; in the
second case it is to be sent in at caution, it being
an additional train.
In many cases it is often difficult for the signalman
to communicate a hand signal to the driver of a train
standing at the home signal. Obstructions to such
signals being seen may arise from another train,
standing on the opposite line, being between the
driver of the train signalled and the signalman, and
in this case the use of a hand signal, especially at
284 RAILWAY SIGNALLING.
night, is liable to be accepted by some other train
than the one it is intended for. In such cases,,
subsidiary mechanical signal arms, or "calling on"
signals, are fixed to the same post as the home
signal, and are used as a signal to proceed at
caution. These signals are, of course, used on the
occasions when the " Line occupied " signal is
exhibited, the ordinary home signal being used when
" Line clear" is shown on the indicators.
It will be observed that this instrument has no
provision for showing the number of trains signalled
into or accepted in the section, and the signalman
at the receiving end must, when conditions exist
which prevent his seeing the whole of the section,
rely upon his train-book for the information upon
which depends his answer to any "Is line clear"
or "Be ready " signal that may be offered for his
acceptance.
Fig. 98 represents a section of line which, between
the points A B, is worked partly by absolute and
partly by the permissive system. The sidings shown
constitute an important goods and mineral traffic
distributing point. The lines between A and B are
rive in number, two of which constitute the main
line, and are worked under absolute block rules ;
two are up and down independents, and are worked
under permissive block rules, whilst the fifth line is
a connecting link between the distributing sidings at
A and a goods centre at B, and is not worked under
any block rules. The construction of the distributing
sidings is not such as to afford room for the shunting
of more than one train at a time, and it is, therefore^
RAILWAY SIGNALLING. 285
286 RAILWAY SIGNALLING.
of some importance to get completed trains out of
the way as quickly as possible. Such trains are
sent to B on the up independent lines, and, being
worked under permissive rules, the traffic is dealt
with in a much quicker and more effective fashion,
since the departure of completed trains from the neigh-
bourhood of the shunting ground is not dependent
upon the absence of traffic on the main line, as it
would be if the independent line did not exist, and
the- trains emerged direct on to the main line at A.
The arrangement is such as to make B the virtual
junction for the distributing sidings on the up side,
with the further advantage that such trains complete
a portion of their journey at the same time as traffic,
which would otherwise delay them, is being carried
on on the main line. Trains emerging on to the
main line at B come under absolute block rules
during their further progress. In a similar way,
trains on the down line enter the down independent
at B, and run direct to the distributing sidings at A,
without further interference with the main line. The
use of permissive block rules for the independents is
obviously of more use for clearing the main line of a
number of trains, at such junctions as A and B, for
more important traffic, than if the independents were
worked under absolute block rules, since a number
of trains may be put on the independent, instead of
waiting till the line was clear of the previous train.
The form of instrument used at the receiving end
of the section between A and B (Fig. 98) is shown
by Fig. 99. This is Tyer's form of permissive block
instrument. Its chief point of difference from the
RAILWAY SIGNALLING.
287-
previous form of block instrument consists in the
provision of means for advising the signalman of
the number of trains in the section at any time.
The commutator carries, inside the instrument, a small
disc, around the circumference of which is painted
" Line closed," "Line clear," "Train on line," "2,"
" 3»" " 4," " 5," " 6." These indications are exhibited
at the lower opening in turn, and in the order just
given. These indications are mechanical, and are
rt=o
o
ft=°
FIG. 99.
shown by turning the commutator handle, and they
are in addition to the indications given by the needle.
It will be observed that only when two or more trains
occupy the section at the same time does the lower
indication differ from that of the needle. The com-
mutator is locked automatically in either of the eight
positions it can occupy, and can only be turned
forward or backward during depression of the small
knob, K, on the right of the instrument. Hence,
288 RAILWAY SIGNALLING.
the movement of the commutator must be made
deliberately, and it cannot be moved without special
intention to do so. The ultimate capacity of a line
on which such an instrument is in use would be six
trains — i.e., six trains might all be between the two
block cabins, A and B, on one pair of rails at the
same time. The instrument used at the sending
end of the section is similar in appearance to
Fig. 99, but it has no commutator or indicator of
the number of trains in the section, and the signal-
man is not called upon to work it in any way.
Another example of the conditions under which
working of traffic under permissive block rules may
CD]
m
FIG. 100.
be of advantage in facilitating traffic over crowded
lines is shown by Fig. 100. On this line there is
a large amount of fast passenger and other impor-
tant traffic between two large and important towns,
one of which is a seaport of some magnitude. In
addition to this traffic there is a large amount of
various kinds, but of less importance, in so far as
time for delivery is concerned. Such traffic has
therefore to give precedence to the more important.
Under the absolute rules considerable delay would
occur, and therefore, in order to cope with the various
classes of traffic, the lines have been doubled for
RAILWAY SIGNALLING. 289
several miles. The original main line is worked
under absolute rules, whilst the up and down inde-
pendent lines are worked under permissive rules.
Trains arriving at one of these junctions, with a
small time margin in front of more important traffic,
may be run upon the independent line alongside the
train for which they have been diverted from the
main line, and may be ready to continue the journey
the moment they arrive at the exit junction. Prac-
tically no delay occurs to either class of train under
these circumstances. Not only is this the case, but
the main line may be rapidly cleared of a number
of trains, since the permissive rules allow of a certain
number of trains being in each section at the same time.
The form of instrument used on the section of line
shown by Fig. 100 for the independent lines is given
by Fig. 101. This represents Hampson's form of
permissive block instrument. The apparatus for both
lines is enclosed in one case. As in Tyer's form of
instrument, indications of the number of trains in the
section are exhibited at the lower opening, in addition
to the dial indications ; the dial signals are operated
by the signalman at the receiving end only ; the com-
mutator and rear section recorder are locked in any
one of the positions it can occupy; and the instrument
is not adapted to transmit descriptive signals of any
kind. As in Tyer's form, all signals, other than the
mere indication of the condition of the line, are made
by a separate bell communication. The instrument is
operated by the withdrawal of the slide, S, which
makes the usual simple commutator changes necessary
to show " Line clear " and " Train on line " on the
19
2QO
RAILWAY SIGNALLING.
dials, and also imparts movement to a sector, passing
behind the lower opening, which is lettered " Line
closed," "Line clear," "Train on line," " i," "2"
" 3," " 4," in order given. Movement of the slide
from one position to the next in order, backward
, or forward, can only be made after depressing and
releasing the knob, K, shown on the right of the
o
1
FIG. 101.
commutator handle. In this respect Hampson's;
instrument differs from Tyer's. In Tyer's form the
commutator must be turned during the time the knob,
K (Fig. 99), is depressed, and it may, under these
conditions, be placed in any of its positions. In
Hampson's instrument the commutator slide can only
be moved after the knob, K (Fig. 101), has beea
depressed and released, and it can then only be moved.
RAILWAY SIGNALLING. 2QI
into the next position, forward or backward, as the case
may be. At the same time there is nothing to prevent
the releasing key of Hampson's instrument from
being depressed any required number of times. The
essential difference between Tyer's and Hampson's
instruments is, that with the former it would be easy
for a signalman to inadvertently turn the commutator
through two positions instead of one ; with the latterr
the recorder can only be made to travel through two-
positions by two distinct operations of the releasing
key, and must therefore be deliberately made.
It will be observed that the method of working with
Tyer's and Hampson's instruments is slightly different
to that described in connection with the instrument
shown by Fig. 97. The difference consists in the
double character of the preliminary signal in use with
the latter form of instrument. The two former move
more nearly on the lines of the absolute block, in so
far as the indications exhibited are concerned : the
latter form labours under the disadvantage of having
two forms of indicator, the needle and the peg, one of
which, the needle, exhibits the same signal whether
the line is occupied by or clear of trains. In addition
to this, it has the defect of not providing any record of
the number of trains in the section at any time at
either end. Tyer's and Hampson's instruments do
provide such indications, up to a prearranged limit
depending upon the instrument, but they only do so
at the receiving end of the section. It is sometimes
contended that it is unnecessary to provide such
indications at the sending end of the section, as the
signalman there has the dial indication to guide
2Q2 RAILWAY SIGNALLING.
him, and, moreover, cannot send a train forward until
the " Be ready," or equivalent preliminary signal, is
accepted by the man at the receiving end. This
contention would be unanswerable if there was
anything of an automatic character in the indications,
or if they depended in any way upon the trains
themselves to act as a check. This, however, is not
the case. The indications of the instrument are
merely records of the movements of the signalman,
and the construction of the locks is not such as will
prevent a signalman from moving a commutator in
such a way as will indicate a less number of trains
than is in the section. If the number of trains in the
section is two, say, and a third is sent in from the other
end, there is nothing to prevent the signalman from
inadvertently moving the commutator to indicate
" Train on line," or " I," instead of moving it so that
it indicates " 3." The instrument at the sending end
would still indicate " Train on line," as it does
whatever number of trains may be in the section,
and there is thus no control or check other
than vigilance in comparing the " Train out of
section " signals with the bookings in the train-book.
The exhibition of numbers, indicating the trains in the
section, at the sending end, worked synchronously
with those at the receiving end, and from that end,
would provide a check against error on the part of the
signalman at the receiving end, which, under certain
circumstances, might be of great value.
Another feature of instruments of the class of
which Tyer's and Hampson's are representative, is an
inevitable difference between the indications exhibited
RAILWAY SIGNALLING. 2Q3
by the instruments, and the actual condition of the
line at a certain stage in the operation of signalling.
The "Line clear" indication is, as already explained,
preparatory, and indicates an intermediate stage
between line occupied and line clear of trains.
Practically, it indicates the conversion of the line
from a neutral condition to a state of preparation
for the reception of a train which is known to be
approaching. An examination of the methods of
working will show that there is no such intermediate
stage in the conversion of the line from the occupied
to the unoccupied state. But in instruments of this
class, where the indications for the exit of the last
of a group of trains must be made in the exact reverse
order to those for the entry of the first of the group,
there must necessarily be a " Line clear " indication
exhibited between " Train on line " and " Line
closed." This, of course, is contrary to the actual
conditions obtaining at the time. The " Line clear "
indication so shown is, of course, exhibited for a short
time only, and is considered of no significance. Such
an indication, however, does not appear on any form
of absolute block instrument. In this respect, Tyer's
form of lock allows of more speedy movement from
"Train on line" to "Line closed," since by keeping
the knob, K (Fig. 99) depressed, the commutator may
be moved at once over the two positions, the needle
giving a mere kick to " Line clear " during the opera-
tion. In Hampson's instrument, the needles must
stand at "Line clear" until the knob, K (Fig. 101),
has been depressed and released a second time, and
the slide pushed home.
CHAPTER V.
MISCELLANEOUS APPARATUS.
Gate Crossing's. — It frequently happens that a
highway crossing is situated between two block cabins.
Such crossings are, of course, provided with a gate-
keeper, but if the crossing is situated on a sharp
curve, or during foggy weather, the gatekeeper has
some difficulty in assuring himself that no danger
exists in opening the gates for vehicles, foot-pas-
sengers, or, worst of all, cattle passing along the road.
Matters were improved by providing the gatekeeper
with an intermediate bell connected in the block bell
circuit, which reproduced all the bell signals exchanged
between the cabins on each side of the crossing. This
method was imperfect, in that the gatekeeper had to
distinguish the different classes of signals from each
other, to rely on his memory after the signals had
passed, and was unable to distinguish between signals
for " up " and " down " trains.
The apparatus now provided on one line is shown
by Fig. 102. The small needle indicators are inserted
in the " up " and " down " block indicator circuits,
and the bell is inserted in the block bell circuit as
before. The gatekeeper has no control over the
instruments, and is not called upon to do any work
in connection with them, but by the aid of the indi-
cators he is able to see, at any time, whether a
train is approaching from either direction, and from
RAILWAY SIGNALLING.
295
the character of the indication, " Train on line "
or " Line clear,'* is able to judge its approximate
distance.
Signal Repeaters. — When signals are not visible
from the cabin from which they are worked, some
means of indicating the position of the arm becomes
necessary. At one time it was customary to fix a
small subsidiary signal in a position where the signal-
man could see it, and arrange it to be worked from
the same wire as the signal it was intended to
represent. Such mechanical repetition had many
J
FIG. 1 02. — Gate Crossing Equipment.
defects, and was unreliable, and electrical methods of
repeating signals were early brought into use.
The forms that signal repeaters have taken at
various times, and in various hands, have been
numerous. Some have been miniatures of the signal
and arm, others have the indications lettered on dials,
and the position of the arm is shown by the relative
positions of the pointer, or the indications exhibited.
Some repeaters show "off" and "on" only. Others
have been made to show "on/' " caution," and "off,"
-.whilst still others show "on," " out of order," and
296
RAILWAY SIGNALLING.
" off." Some forms of repeaters require two wires,,
but the majority only require one ; some forms require
continuous currents to maintain the "on" positions,,
others to maintain the "off" position, whilst still
others require continuous currents for both " on " and
"off." The disc indicator, shown in Fig. 103, requires
continuous currents for both "on" and "off"; the
semaphore form shown in the same figure requires
a continuous current to maintain the " on " position,
whilst the needle form of indicator shown by Fig. 106
FIG. 103.
Semaphore Distant Indicator. Disc Indicator with Plug Switch.
requires continuous currents for the "off" and "out
of order " positions.
The construction of the contact boxes at the signal
for providing the necessary indications is naturally
governed by the character of the indications decided
upon as desirable. An earlier form of contact box
and the method of fixing is shown in Fig. 104, where
the movement is obtained from the rod at a point
between the counterweight and the arm. In this
method the indicator shows two positions only —
" on " and "off," the " on " position being the normal
RAILWAY SIGNALLING.
297
indication when no current was passing, and the " off"
being maintained by a continuous current.
Consideration of the conditions of working shows
that such an arrangement lacks the reliability so
important a piece of apparatus should have. In the
first place, the point indicated is not that of the arm
itself; in the second place, the apparatus is self-
INDICATOR & BATTERY
IN CABIN
FIG. 104.
testing in one position only. If the rod working
the signal arm broke between the contact box and
the arm, or if the key fixing the arm to the spindle
slipped out, the arm would indicate "off" whilst
the electrical repeater would be showing " on."
Further consideration shows that the relative posi-
tions of the signal lever, signal arm, and electrical
2g8
RAILWAY SIGNALLING.
repeater are of great importance, and that there
exists a great necessity for the repeating apparatus
being self-testing in the " on " position. If the
signal arm is " on " when the signalman expects
it is "off" no accident is likely to occur, and slight
delay to traffic is the only probable consequence.
If, however, the signal is "off" when the signalman
UNE
FIG. 105. — Signal Indicator Contact Maker.
•expects that it is " on " the consequences may be
very different, since it is the signal arm which
-ultimately controls the passage of traffic, and all
other apparatus, mechanical or electrical, are merely
accessories used to ensure the exhibition of the proper
•outside signals for the time being.
The forms of contact box shown by Figs. 105 and
RAILWAY SIGNALLING.
2Q9
io6 are fixed concentrically with the spindle of the
signal arm, and obtain the motion from the move-
ment of the spindle. They are used in connection
with the needle form of repeater shown in Fig. 106.
With this form of repeater three positions are shown —
"on," "out of order," and "off"; and Fig. 106 is
drawn to show the " out of order " position. This
indication, as will be seen, is an intermediate one
CONTACT MAKER ON SIGNAL AKM
S.N.DISTANT INDICATOR
FIG. 106.
between the "on" and "off" positions of the arm,
and must be passed over each time the arm passes
from "on" to "off," and vice versa. The chief use
of this indication is to show that the signal arm
is fully "on" or "off." An "out of order" signal
would be shown on the electrical repeater instead
of an "off" signal in one case, or an "on" signal
in another case, if the wire working the signal has
300 RAILWAY SIGNALLING.
become slack or tight from expansion or contraction
respectively, and such an indication would be inter-
preted by the signalman as indicative of the necessity
for regulating the wire working the mechanical signal.
It will be noticed that the movement indicated is
not that of the arm but that of the spindle ; and
that the removal of the key fastening the arm to
the spindle would allow the signal arm to fall,
without effecting a corresponding change of position
of the electrical repeater. It is true that the position
the arm would take up under these circumstances
would, if noticed by a driver, be regarded with
suspicion, but it should not be forgotten that it is
the signalman for whom the repeater is provided,
and he would have no notification of the position of
the arm being other than that corresponding to the
position of the lever working it.
The " out of order " indication of the form of
electrical repeater shown in Fig. 106 is of some
interest when its significance is understood, and the
limitations imposed by the form of instrument and
the method of using are considered. As has been
stated, the "out of order" indicates a discrepancy
between the relative positions of the signal arm and
the lever, and so far it is a true " out of order "
indication. Whilst this is so, it will be observed
that, owing to the repeating apparatus not being
self-testing in the " on " position, conditions may
easily arise where the indication of the electrical
repeater may differ from the actual position of the
arm, and the latter differ from the position of the
lever. Further, a defect in the repeating apparatus,
RAILWAY SIGNALLING.
301
"on," affords no
if it occurs when the signal is
indication of its existence to the signalman.
To the writer it seems unsound to treat the signal
and the repeating apparatus as different pieces of
apparatus. Rather, it seems, that they should be
considered as one, and the " out of order " signal
should be such as not only indicates a discrepancy
between the positions of the arm and lever, but also
a defect in the repeating apparatus. In short, an
efficient repeating apparatus should do, for a signal
FIG. 107.
which is out of sight, all that a signalman can do
for himself in connection with a signal within sight.
Another form of contact-maker, and the method of
attaching to the signal, is shown by Fig. 107. It is
used in conjunction with the disc indicator shown in
Fig. 103. The "on" and "off" positions are both
maintained by continuous currents : if from any cause
the circuits are broken, the indicator takes up an
intermediate position as shown in Fig. 107. This
form would appear to possess considerable advantages
3O2 RAILWAY SIGNALLING.
over the forms shown by Figs. 104, 105, and 106, in that
the movement indicated is that of the arm itself, and
the apparatus is self-testing in any position. The
intermediate position shown by Fig. 107 is a true
"out of order" signal, and is shown not only when
the arm occupies a different position to that of the
lever, but also when a defect occurs in the electrical
repeating apparatus. A small peg switch is provided
by which the circuit may be disconnected during such
times as the signal is not being used, in order to
prevent the batteries being run down unnecessarily.
As the Board of Trade inspectors require signal
indicators to be fixed in plain sight, and immediately
opposite the lever working the signal, there is not
much danger of the absence of the peg being
unnoticed when the apparatus is being brought into
use. At the same time, combinations of circumstances
may arise in which the absence of the usual indication
would be undesirable.
Signal Light Indicators. — During darkness, the
arm of a signal post is replaced as a signal to drivers
by a light, which is invariably red for " danger," and
is green, or white, when the line is clear for an
oncoming train. Where signals are at a distance
from the cabin, and the back lights are not visible,
the existence of the light is indicated.
The apparatus employed for this purpose is of a
simple character, and is shown by Fig. 108. It con-
sists of an expansion bar, a, formed of an iron rod
passing through a copper tube which is fixed above
the flame of the lamp. The difference in the
coefficients of expansion of iron and copper cause
RAILWAY SIGNALLING.
303
the former to exert a pull on the short end of the
lever, 6, and separates the contact points. The
expansion bar is connected to a small make and
break bell and battery, placed in the cabin, by a
special wire. If the light goes out from any cause,
the expansion bar cools, and the bar, 6, is brought
into contact with the terminal base, and the bell
begins to ring and will continue to do so until the
light is re-established. A small peg switch is
Copper
^ Tube f Iron Rod
FIG. 108. — Light Indicator.
provided, so that the circuit may be disconnected
during the time the lamp is not required to be alight.
In other cases the bell is supplemented by an.
indicator showing " Light in " and " Light out."
The " Light in " signal is maintained by a continuous-
current, and the indicator circuit is arranged as
a shunt on the bell connections, as shown in Fig. 109.
In this way the bell is rendered silent during the
time the indicator shows " Light in " ; but should
the light go out or anything occur to interrupt the
304
RAILWAY SIGNALLING.
circuit, the continuous ringing of the bell draws the
signalman's attention to the new position of the
indicator.
"Distant" Signal Lights. --- The form of the
arm of a "distant" signal is slightly different to
that of " home " or " advance " signals in being
cut at the outer end, as shown in Fig. 104. This
difference in form is made in order that the difference
FIG. 109.— Diagram of Connections for Continuous-Current Light
Indicator.
in the signals may be more easily identified, and to
accentuate the difference existing in the character
of these signals. " Distant " signals are passed
whether " off " or " on " ; " home" or " advance "
signals must not be passed under ordinary circum-
stances when "on." The two latter signals are
essentially " stop " signals ; the former is not.
In order that a similar distinction may exist between
RAILWAY SIGNALLING.
305
the lights of " distant " and other signals, the apparatus
shown by Fig. no is being introduced by Messrs.
Stevens and Sons, the railway signal engineers, for
the purpose of changing the fixed light now in use
to one of a " flashing " character. The lamp is of
the usual construction, but in front of the light is
FIG. no. — Distant-Signal Flash-Light Mechanism.
placed a circular disc, a, to which an oscillatory
movement is imparted by the motion of the armature
of the electromagnet, E. The apparatus is of a
simple make and break character, the interruption
of the circuit taking place between / and g. A
circular hole is cut in the disc, a, at h, and this
20
306
RAILWAY SIGNALLING.
is placed on a level with the flame of the lamp.
The movement of the disc causes the light to be
alternately covered and uncovered, the return motion
being obtained by the aid of the greater weight of
the lower portion of the disc.
As already intimated, the apparatus is as yet only
in the experimental stage, and it is therefore too
POINTS INDICATOR INC ABIN
To Sid inf.
FIG. in.
early to discuss its suitability or otherwise. At the
same time it may be said that signals fitted with
such an apparatus, as at present constructed, would
require to have the " flashing " indicated in the
cabin, in addition to the indicating of the existence
of the light. Moreover, the "flashing" would require
indicating for signals which under ordinary circum-
stances are in plain sight, for the reason that the
RAILWAY SIGNALLING. 307
apparatus does not " flash " the back light, which is
the only part the signalman can see.
Points' Indicators. — It sometimes happens that
" points " are placed in positions where they cannot
be seen by the signalman. In such cases the
apparatus shown by Fig. in is sometimes used.
Indicating: the Section between Cabin and
" Advance " Signal. — It frequently happens that
whilst the arm of an " advance " signal is visible
from the signal cabin, owing to its being placed on
a comparatively high post, the base, and a part of
the line cannot be seen on account of some object,
such as a bridge crossing the line, intervening. In
such cases there is a possibility of a short train,
standing at the " advance," being forgotten, and
another train being sent into its rear. The apparatus
shown by Fig. 112 is intended to minimise the danger
arising in this way by indicating a section of the line,
which commences somewhere near the cabin, and
terminates at a point a little beyond the " advance "
signal.
The apparatus consists of two rail contacts fixed
at selected points, and an indicator. Line wires are
run to each rail contact. When a train passes over
the first rail contact the parallel bar is displaced by
the flange of the wheel, and the magnet, E, is
energised by current from the battery, F. The
armature of E is attracted, and the rocking bar, b,
falls, locking the armature, and thus maintaining
the local circuit through the battery C, d, and the
indicator coils, and displaying the signal, " Section
to ' advance ' blocked." When the train passes over
20*
308
RAILWAY SIGNALLING.
RAILWAY SIGNALLING. 3OQ
the second rail contact the electromagnet, E, is
energised by the current from the battery G, the
rocking bar is raised and the armature of E released,
the local circuit of the battery C is broken and the
needle of the indicator points to " Train passing out
of section," which indication is maintained until the
last vehicle, in motion, has passed over the rail con-
tact. The normal position of the needle, when no
current is passing, is " Section to ' advance ' clear."
The knob, a, at the side of the instrument is pro-
vided for the mechanical release of the rocking bar, 6,
from the position indicating " Section to ' advance '
blocked " for cases where a train, having passed
over the first rail contact, has shunted into a siding
without having passed over the second. This last
arrangement detracts somewhat from the value of the
apparatus as an automatic arrangement. It will be
noticed that there are three batteries to provide two
deflections only. The work of the local battery, C,
might, with a slight rearrangement of the connections,
be performed by the battery F.
Rail Contacts. — Rail contacts are not as yet so
important a feature of railway signalling as they are
probably destined to be, when the apparatus used
assumes a more automatic character than it possesses
at present. One form of rail contact is shown by
Fig. in, in which the flanges of the wheels of a
passing train are made to impart a horizontal move-
ment to a bar laid parallel with and close to the rail,
the return motion being obtained by a massive spring
acting against the motion imparted by the train.
Most rail contacts, however, are made to take advan-
RAILWAY SIGNALLING.
tage of the deflection of the rail by the weight of a
passing train, in order to obtain the movement neces-
sary for an intermittent connection. Several forms of
rail contact suggested and used for various purposes
are shown by Figs. 113, 114, 115, 116, 117, and 118.
FIG. 113.
Rail contacts differ slightly in accordance with the
character of the signal they are intended to provide
for. Some forms only make contact during the time
the rail is sufficiently depressed ; others make contact
FIG, 114. — Circuit Broken.
for a longer period. Figs. 113 and 114 are examples
of the first ^division. In the form shown by Fig. 114
the two connecting wires are sealed into one end of
small chamber containing mercury, and the link work
RAILWAY SIGNALLING.
is arranged so that the mercury covers the ends
exposed inside the chamber when the rail is pressed
down. In this form a deflection of the rail of Jin.
is sufficient to make the necessary contact. Owing
to the small deflection required, the outer lever is
practically steady during the passage of a train.
Fig. 115 is an example of the form of rail contact,
by which a more prolonged contact is obtained. The
contact-making apparatus consists of two mercury-
FIG. 115. — Circuit Closed.
'Cups to which the wires are connected. When the
rail is depressed, a metallic bridge-piece dips into the
mercury-cups, and completes the circuit. The lever
arm carrying the metallic bridge is pivoted at or near
its centre, and carries at the opposite end a semi-
circular, perforated bowl, which under normal con-
ditions dips into a vessel containing paraffin oil.
When the rail is depressed the bowl is raised into the
.position shown, and is emptied of oil at the same
312
RAILWAY SIGNALLING.
time. When the train has passed over and left the
plunger free the bowl slowly fills with oil and sinks,
and by raising the metallic bridge out of the mercury-
cups breaks the circuit. By proportioning the number
and size of the perforations, a contact for any desired
length of time may be obtained.
Another form of mercury contact-maker, shown by
Figs. 116 and 117, is that used by Messrs. Saxby and
Farmer in connection with their system of interlocking
the mechanical "advance" or "starting" signal with
FIG. 1 1 6.— Buck's Patent Rail Contact.
the block instrument. In this form the vertical
motion of the rail is made to impart a horizontal
motion of the mercury-cup, and the alteration of the
level of the mercury brings it into contact with the
curved metallic bridge seen in Fig. 117. The lever
worked direct from the rail is locked with it, as will
be seen from Fig. 116, and the return motion is also
imparted by the rail.
Siemens's form of rail contact, shown by Fig. 118,
is capable of giving a more or less prolonged contact
RAILWAY SIGNALLING.
by the depression of the rail. In this form mercury
is also used to make the contact, and it is pumpedr
by the deflection of the rail, to a slightly higher level
than the normal, in order to bring it into contact
with the projected connection to which the line wire
is connected. The spring-plate, 6, is flexible, and on
the deflection of the rail the mercury is forced up the
tube, h, and into the small chamber, c. When the
FIG. 117.— Buck's Pau:it Rail Contact.
rail is released, the mercury runs through the hole, sr
into the larger chamber and >reaks the circuit. The
difference in the levels of the mercury in the large-
chamber, and under the spring-plate, b, ensures the
latter keeping the plunger, P, in contact with the
under side of the rail, when the latter is not depressed.
An indiarubber ring, a, is pi; iced under the rail in
order to exclude dust or grit which might impede
314
RAILWAY SIGNALLING.
the free working of the plunger. The apparatus is
shown attached to a flat-bottomed rail, but it would
equally be as easily fixed to one of the ordinary
•double-headed form.
Considering the forms of rail contact shown, and
some of the duties they have, or may have in the
future, to perform, it will be seen that they are, as
(has often been pointed out, defective, in that the
first vehicle passing over the contact performs the
'duty which should be done by the last. " Last
FIG. 118.— Siemens's Rail Contact.
vehicle," in this case, implies something more than
the last which passes a certain point, since it is
quite possible for a train to divide and one portion
to be left standing in such a position as constitutes
it a danger to a succeeding train.
Consider, by way of example, the case for which
the instrument and arrangement of rail contacts
shown by Fig. 112 is intended, and assume that a
short train is standing at an " advance " on a sharp
curve, and out of sight of the signalman. So long
RAILWAY SIGNALLING. 315
as no part of the train has passed over the second
contact, the indicator will remind the signalman of
the presence of the train ; but if only a part of the
train passes over the contact, the indicator will
ultimately show " Section to advance clear." Under
these circumstances the signalman would be justified
in sending a succeeding train forward. It is true
that the driver of the train is supposed to see that
he has got the whole of his train with him, and it
is also true that the guard on seeing a part of the
train proceed forward should take steps to protect
the part left standing ; yet it is undeniable that most
curious and, apparently, improbable combinations of
circumstances are constantly arising. In any such
event as that outlined, the indicator would be showing
an incorrect signal.
It is, of course, a comparatively easy task to pick
out defects in any form of apparatus intended for a
specific purpose under varying conditions. These
remarks, however, are only intended to show that
the apparatus in use on railways for certain purposes
is, in some cases, still in the evolutionary stage.
Where rail contacts, of the forms shown in Figs.
69 and 1 12-120, are intended to actuate apparatus
which gives indications of the nature of " Line
clear," they would appear to be ineffective, in that
they are unable to differentiate between the last
vehicle of a train and any of the preceding vehicles.
In order to ensure the fullest possible protection
to trains from apparatus, such as is shown in Fig. 112,
or other apparatus indicating " Line clear," the last
vehicle of every train should be capable of performing
RAILWAY SIGNALLING.
some duty that cannot be done by any other vehicle
of that train. This, of course, involves the last
vehicles being of a distinctive character to the
others, or provided with an attachment which shall
be capable of performing for the indicating instru-
ments the same function the tail lamp, or other
" Last vehicle " signal, does for the signalman.
FIG. 119. — Hollins's Rail Contact.
Sykes's form of rail contact is shown by Fig. 6gy
and it is characteristic of the thoroughness of the
arrangements made to obviate failure by Mr. Sykes
in all apparatus of his devising. The contact is made
by the tilting of two mercury-cups, by the depression
of the rail ; the object aimed at in the use of two
contacts being to secure immunity from total failure
RAILWAY SIGNALLING. 317
in the event of one of them being defective, in the
same way that two independent batteries are pro-
vided for the operation of his block instruments, as
shown by Fig. 71.
Another form of contact maker, described by Mr.
F. T. Rollins, of the Great Eastern Railway, in a
paper read at a recent meeting of the Institution of
Electrical Engineers, is shown by Fig. 119, which
gives a side view of the apparatus, and also an end
view of the contact maker. The tail-piece, 2, fits
into a hole in the web of the rail, and is keyed by
C/utch ftd// Contact
on end of Levor
/net
Lever
FIG. 120.
the adjustable steel key, 3. The contact is made by
4, which is carried by a friction clutch, 7, which,
again, slides on the steel bar, 8. The motion of
the contact maker and friction clutch is limited by
the stops, 5 and 6. The position of the contact
maker on the steel rod, 8, is therefore capable of
being automatically adjusted to suit the
UNIVERSITY
RAILWAY SIGNALLING.
of the road, by the passage of trains over the rail-
to which the treadle is attached.
In order to prevent premature action of the raiF
contact, Mr. Hollins insulates a rail at the point at
which the treadle is fixed, and arranges the circuit
Contact M&A&-
Top we*
FIG. 121.
of the unlocking current so that it is completed only
when -the insulated rail (Fig. 120) is joined to the
opposite one, which, of course, occurs when any
vehicle passes over that portion of the line.
Figs. 121 and 122 show Sykes's electric fouling
RAILWAY SIGNALLING.
bar, which is used to ensure that no portion of a
train, which has been shunted into a siding, is in
such a position as is likely to entail danger to a
train which may arrive on the line with which the
siding is connected. Where trains are shunted into
a siding instead of passing over the releasing treadle
near the advance or starting signal, a second or
more treadles are required in proportion to the
number of points at which trains may be turned
from the main line. Under such conditions the
second treadle must be placed at some point in the
siding, and the point at which release is to take
place is not easy of selection, under ordinary condi-
tions, owing to the great difference in the length of
trains. Fig. 121 is a plan of the electric fouling
bar, and Fig. 122 is a longitudinal section. The
bar, 3, is depressed by the flange of the wheel of
any vehicle, and this motion is imparted to the
rod, 6, and causes the contact, i, to be broken.
The circuit of the treadle (which may be placed
anywhere further in the siding) is completed through
320
RAILWAY SIGNALLING.
•the contact, i, and depression of the treadle can only
•release the lock of the instrument when the contact,
i, is complete. The bar, 3, is sufficiently long to
•ensure its being depressed by at least one wheel of
any vehicle, and thus prevents the contact, i, from
FIG. 123.
being closed until the last vehicle entering the siding
has cleared the fouling bar.
Another piece of apparatus described in the paper
by Mr. Hollins, already referred to, is Sykes's signal
selector, which is shown by Fig. 123. The apparatus
"RAILWAY SIGNALLING. 321
is intended for use where a number of signals are
vfixed upon one post, and provides for the working of
any one of the signals by one lever, the signal arm
lowered on any occasion being dependent upon the
position of the points. As will be seen from the
diagram of connections (Fig. 123) a line wire is run
from each set of points to the signal post, and a
battery wire to all the points contact boxes, the
latter being in series. When all the points are as
shown, the circuit is completed through the most
distant point box, and operates the signal for the
straight road. If the most distant points are set
for a train to pass to that branch, the circuit for
that signal arm is closed, and so on for any other
points connected with the arrangement.
The movement of the lever in the cabin raises
the rod, /r, on the post. This rod is connected to
the middle of as many horizontal levers as there are
arms to be operated. One end of each horizontal
lever is attached to the rod which operates the
particular signal arm it is intended for. The other
end of each horizontal lever is connected with the
selector, and when the circuit from any pair of
points is closed, and a current established, the
selector fixes the end of the corresponding hori-
zontal arm. Subsequent movement of the rod, r,
•causes the end of this horizontal lever, to which
the rod operating the arm is connected, to move
upwards and lower the arm.
The operation of any of the arms depends upon
the points being properly closed for the line which
:is controlled by the arm which it is intended to
21
322
RAILWAY SIGNALLING.
RAILWAY SIGNALLING. 323
lower, and the apparatus thus becomes a points'
indicator. Apart from this, however, it forms no
part of a safety device, since, as will be observed
from the diagram of connections, it, obviously,
depends upon the mechanical interlocking between
the different points' levers to prevent more than one
road being set at a time.
A novel and interesting application of electrical
interlocking, also described by Mr. Hollins, is in use
on the Great Northern Railway near King's Cross
Station. The arrangement is shown diagrammatically
by Fig. 124.
R! and R2 are polarised relays, R4 is a non-polarised
electromagnet connected across the rails through the
tunnel, which constitute a section insulated, electri-
cally, from the rails at either end of the section. B3
is a battery of low electromotive force connected per-
manently with the insulated section of rails as shown.
B.2 is a battery, the middle point of which is con-
nected with the slot indicators at Belle Isle, and, by a
line wire passing through the tunnel, with the relay R19
the slot indicators, bell, and the armature of R2 at
King's Cross West.
When Belle Isle pegs the block instrument needles
to " Line clear," the current passes through the coils
of R2, and closes the contact a. Belle Isle next lowers
one or other of the two signals " Belle Isle Down Main
Home," " Belle Isle Down Main to Goods Home," as
may be required. The movement of the arm com-
pletes the circuit of one of the sections of the battery,
B3, the current from which divides at i, again at 2,
and again at 3. At i, part of the current goes through
21*
324 RAILWAY SIGNALLING.
the slot indicators at Belle Isle, and the remainder
to King s Cross West by the line wire. At 2, part of
the current passes through the relay, R2, to earth
through the contact d, the remainder passing to 3.
From 3 the current branches through the bell and
slot indicators in parallel direct to earth, and through
b, a, M, and C to earth at d. The action of the latter
portion of the current releases the lever lock by
energising M and releases the signal lever, L, which
may then be pulled into the " off" position.
Movement of L reverses the position of the double
contact, C, and the circuit from 3 through b, a, and M
being broken, the lever lock is replaced in position for
engaging with L when the latter is returned into the
" on " position.
The current passing through Rx sets up a current
from Bj which passes through one or other of the
Sykes signal replacers, S S, according to the direction
•of the current through the coils of Rlf and passing
by C, after L is moved into the " off" position, lowers
the signal arm by the action of the replacer.
When the block indicators are indicating " Train on
line " the contact a is broken by the reversal of the
armature of R2, and the lever lock is not affected by
M even if the lever, L, is in the " on " position.
When the engine or train previously signalled enters
upon the insulated section of line at the King's Cross
end, the battery B3 is short-circuited through the
wheels and axles of the vehicles, and the armature of
R4 being no longer held, breaks the contact d. This
breaks the current set up from B2 by the lowering of
the arm at Belle Isle, which has been passing through
RAILWAY SIGNALLING.
325
Rlf and consequently breaks the current through the
signal replacer, S, affected, which then places the
signal to danger behind the train. Hence, as long as
a train occupies any portion of the insulated section
of rail the circuit of Rj is broken, and the signal
replacer, S, cannot be actuated, since no current can
Transmitter. Receiver.
FIG. 185.— Block Bell and Telephone Circuit.
be passed through Rlt even under such conditions as
obtain when the block indicators are exhibiting " Line
clear," and, the lever lock being released by M, the
lever, L, is pulled into the " off" position.
It will be noticed that the lever, L, operates either
326 RAILWAY SIGNALLING.
of the signals, and that it can only be pulled into the
" off" position after the receiving signalman has given
permission for an approaching train to enter the
section.
It will also be noticed that the signalman at Belle
Isle really controls and decides which of the two
signals at King's Cross West shall be operated by the
movement of the lever, L, at the latter place, whilst
the battery B3 can only maintain the circuit by
which the signal arms are actually brought into
active operation during the time the insulated
section of the line is unoccupied.
Telephones on Block Circuits. — The extensive use
of telephones on railways has led to the trial of
combined circuits for telephones and block bells,
the latter being selected because the currents used
for bell signalling are transient only. A form of
switch used for this purpose is shown by Fig. 125.
The arrangement, of course, admits of being used
between two successive cabins only. The block bell
is used as a means of call to the telephone.
CHAPTER VI.
GENERAL CONDITIONS.
It may be useful to recapitulate some of the chief
conditions which experience, and the general trend of
development, indicate as necessary, and it may also
be of some interest to see in what degree the most
modern apparatus is calculated, if adopted generally,
to secure immunity from errors of a similar character
to those which are known to have been the direct
cause of some of the more recent accidents. It is
only by the study of the combinations which make
for or against the object aimed at that the knowledge
usually denominated " practical " is obtained, and
it is commonly acknowledged that the experience
acquired from failure is most completely assimilated.
The chief causes contributing to accident have
already been referred to. They may here be briefly
summarised as follows : (i) acceptance of a train
into a section which is already occupied ; (2) sending
a train into a section already occupied ; (3) failure to
notice the positions of the fixed mechanical signals.
These deviations from the rules under which block
working is carried on, have all at one time or another
been the first cause of accident.
The three causes enumerated cover the possibility
-of error on the part of the three responsible persons
-engaged in the working of any train through a block
section worked under absolute rules — viz. : (i) the
328 RAILWAY SIGNALLING.
signalman at the receiving end ,- (2) the signalman^
at the sending end ; (3) the driver of the train-
passing into or out of the section. Of these three
persons the first is usually considered as holding the
most responsible position, since it is he who, under
the ordinary working conditions, accepts or declines-
to allow trains to enter the section at the opposite
end, according to the condition of the line at the
time. There is no doubt that when working strictly
to regulations, the signalman at the receiving end is
in a position of great responsibility, since, before
accepting any train, he must assure himself that the
whole of the preceding train has cleared the section,
and that no obstruction exists, at his own station,
which involves possible impediment to the approach-
ing train throughout the whole length of the section
it has entered, or is about to enter. A. failure in
observing this most elementary rule of block working
led to a most disastrous accident on- one of the
leading railways about four years ago, and resulted
in considerable loss of life under most lamentable
conditions, and in great destruction of property.
During the time that work is carried on in accord-
ance with the rules of the service, the sending signal-
man's responsibilities are confined to the exhibition,
of the proper mechanical outdoor signals for the
information of the driver of any train which may
approach, and generally acting in accordance withi
instructions received from the other end of the
section. If, however, any deviation from the usuaL
method of working occurs, either from negligence or
inadvertence, it is just as likely to originate at the
RAILWAY SIGNALLING.
sending end as at the receiving end, and the results
may be equally disastrous. There is no lack of
instances where trains have been sent forward under
the impression that the indication of the block-
instrument refers to that train, and the lowering of
the signal at the proper time has been neglected..
In other instances trains have been sent forward
without any of the usual block signals being
exchanged, and the signalman at the receiving end.
has had no intimation of the train until it came
under his personal observation.
In so far as the acceptance of a second train into
an absolute block section is concerned, apparatus of
a similar nature to that shown by Fig. 44, Saxby
and Farmer's (Figs. 49-61), or Sykes's (Figs. 62-71),.
in which the receiving instrument is locked to " Train,
on line" until the train signalled has passed a certain,
point, or one of a number of points at relief sidings
or junctions, would appear sufficient. To be con-
sistent, however, the arrangements should be com-
pletely automatic, and this, of course, involves the
use of releasing treadles at each of the points at
which a train may clear the section, and other
means of cancellation than exist at present.
In so far as the sending of a second train into a
section is concerned, such arrangements as are shown
by Fig. 45-48 (Winter's), Figs. 58-60 (Saxby and.
Farmer's), or Fig. 70 (Sykes's), in which the signal,
controlling the advance section is locked until the
"Train on line" or "Line clear" signal is accepted,,
and is automatically replaced to "danger" by the
passage of the train into the section, are a great
33° RAILWAY SIGNALLING.
advance on the usual method of working, and should
be sufficient to prevent such errors. These methods
have the further advantage of not interfering with the
usual method of working traffic, or requiring the line
to be cleared for a greater time than ordinary for
an approaching train. This, of course, is a matter
of considerable importance in the working of busy
functions.
In cases of non-automatic working, a point of some
^importance arises on further consideration of the two
probable causes of error just referred to. In one case,
"•the acceptance of a second train may be made under
the impression that it has been forgotten to clear the
line for the last train. On the other hand, as has
been shown, a train may be sent into a section under
a similar misapprehension. In neither case does the
ordinary form of instrument afford any indication of
the deviation from the regular methods of working,
and any attempt to avert the consequences arising,
must depend upon the signalman remembering the
conditions actually existing, and, recognising his error,
taking such steps as are possible under the circum-
stances. Certainly, some such intimation might be
of the greatest possible utility to the signalman at the
receiving end of the section ; and it is quite con-
ceivable that, under certain circumstances, prompt
action on the part of the receiving signalman, as a
consequence of an automatic indication of the
presence of two trains in the section, might enable
him to avert the consequences of the error, by allowing
.the first train to draw within the protection of one of
.the stop signals. Such apparatus need be of the
.RAILWAY SIGNALLING. 331
simplest possible construction, but, owing to its casual
use, would require to be carefully maintained in
working order.
If the third contributory cause of error — failure to
notice the position of the fixed mechanical signals —
.is considered, it will be observed that there is not
anything like the number of devices in use, or
suggested, to protect the driver from possibility of
error. With some exceptions the driver is the only
person of the three concerned who has, practically,
been left to depend upon himself. Whilst this is
the case, neither of the signalmen are in such a
position of responsibility as the driver. Errors on
the part of either of the signalmen may be minimised
and accident averted by vigilance and promptitude
on the part of the driver, and have been on many
occasions. If, however, the driver errs and runs
past the signals, the signalmen have no control
over his actions whatever, and are powerless to
avert the consequences. It cannot be too strongly
insisted upon that block signalling is only a means
to an end, and that end is the exhibition of the
proper signals for the guidance of the drivers of
trains. If the necessity for automatic control of the
means of signalling to the driver is felt, and the
general line of progress is sufficient to prove this,
how much more important is it that special means
should be provided to ensure that the person, for
whose guidance the whole system of signalling is
devised, is really made aware of the conditions under
\vhich he is running at any and every point where
signals are exhibited.
332 RAILWAY SIGNALLING.
A big smash on one of the leading lines a few
years ago, was directly traceable to failure on the
part of the drivers of the train to observe the
positions of the mechanical signals at the entrance
to the section in which the collision occurred, owing
to the prevalence of fog. One of the two drivers
of the train which ran past the signals paid for the
error with his life, and the other with the loss of a
limb. It is true, of course, that railway companies
have elaborated arrangements for replacing the usual
visual signal by aural equivalents in the event of a
fog, or other similar cause, preventing the former
from being available. For the period of the intro-
duction of fog signalling, it was no doubt eminently
suitable, but for the present period it leaves some-
thing to be desired. In the first place, the indication
to the driver that the line is clear, and signals, which
he cannot see, are off for his advance, is of a negative
character only. The absence of an explosion, due to
the engine passing over one or more fog signals, is
taken as an indication that the line is clear to pro-
ceed. Under this condition the driver has no real
assurance that fog signalling has been commenced.
Again, the fog signals have, in the ordinary form
of working, to be placed in position by men stationed
at the signals, and these men must take the position
of the arm as a guide to their own actions in placing
the fog signals to be exploded, or removing them,,
according as the signal arm is " on " or " off." The
control of the section of line protected by the signal
is dual, and therefore, whilst there may be two*
possible checks against error, there are undoubtedly
RAILWAY SIGNALLING. 333
two points at which error may arise. Further, the
calling out of the fogmen for their special work
depends under the present system, in many instances,
upon the signalman, and he must exercise his judg-
ment upon the necessity, or otherwise, for calling
out these men as occasion may require. Some time
may elapse between the decision to commence fogging
and the actual commencement, more especially during
the night. During this interval the necessity for the
fogmen may increase, or it may cease altogether. In
the first case the signalman may think he has delayed
calling out the men too long, and in the other case
he would think his action was premature. In either
case his position is not a comfortable one.
Many attempts have been made to provide auto-
matic, or semi-automatic, means to warn the driver of
the positions of signals he is approaching or passing,
under conditions which prevent their being seen ;
and railway companies are by no means backward
in giving a trial to apparatus which possesses any of
the elements necessary to success. Some forms of
apparatus for this purpose are adaptations of the
ordinary fog signal to use, at any time, by the aid
of mechanical means, by the signalman working the
signal. Usually a number of fog signals are kept in a
special case near the signal, and the signalman, by
the use of a special lever in the cabin, communicating
with the box by a wire, is able to place a fog signal
near the rail, on a specially prepared base, for
explosion by the depression of a rod over which the
train passes. The ability to commence using the fog
signal at any time is a great advantage.
334 RAILWAY SIGNALLING.
Unless, however, the apparatus is duplicated, only
one fog signal can be put in position at once, and in
the event of its not being exploded, from any cause,
the results may be serious. Moreover, the adjustment
of the fog signal in position for explosion is somewhat
fine for operation, at such a distance as " distant "
signals are usually placed, by the aid of a wire which
is subject to alterations of length with varying tem-
peratures.
Electrical methods have also been suggested for
this purpose. Some of these involved the use of a
bell fixed on the engine in any convenient position.
This bell was to be operated by a battery, also
carried on the engine, the circuit being closed by
an obstruction placed by the side of the line, which
was operated by simple means in conjunction with
the signal to be indicated. This arrangement was
not reliable on account of the difficulty experienced
in maintaining batteries in a state of efficiency under
the conditions of their use, and also on account of
the vibrations and shocks to which the apparatus
was subject. Other arrangements involved the use
of a large bell, fixed in proximity to the line at a
suitable height, which was intended to ring con-
tinuously whilst the signal was " on," and which
could be put out of operation when not required
by the use of a small peg switch. Such arrange-
ments are of little use for the purpose intended;
the difficulty of conveying sounds from the outside,
to the inside of the cab of an engine in rapid
motion, are immense, and can only be appreciated
after experience.
RAILWAY SIGNALLING.
335
Suggestions have also been made for repeating the
position of the signal arm directly on the engine by
mechanical means, worked in conjunction with the
signal. One of these methods, suggested by the
author about four years ago, is shown by Figs. 126
and 127. The apparatus on the engine for indicating
the position of signals consisted of a small fac-simile
FIG. 126.
of the ordinary outdoor signals. This was fixed on
the cab of the engine, as shown. A counterbalance,
W, was fixed to the arm, so that when not otherwise
supported the latter took up the " on " position. To
the frame of the engine was pivoted a metallic
rectangle, R, arranged to turn on its upper side as
an axis. A rod, bifurcated at its lower end to engage
336 RAILWAY SIGNALLING.
with pins, />, on the rectangle, R, passed then to s, and
supported the arm in the " off" position under normal
conditions. Movement of the rectangle in either
direction caused the support to be withdrawn from the
arm of s, and it at once took up the "on" position
]by the action of the counterbalance. As will be
noticed from Fig. 126, the arm could only be replaced
in the " off" position by the direct action of the
driver.
The great difficulty in connection with the design
•of apparatus for this purpose, is the violent shock
^experienced when used on trains travelling at a high
FIG. 127.
rate of speed. In order to minimise the shock, the
swinging rectangle, R, was operated by sliding over
the inclined bar, B (Fig. 127), which was fixed in the
^centre of the four-foot way, and one end of which
was raised, or lowered, as the signal was " on " or
"off." When the signal arm was "off" it was, of
course, intended that the bar, B, should be in such
.a position as would prevent its operating upon
the swinging rectangle, R.
The fixing of such a means of operating an
indicator on the engine requires considerable care
RAILWAY SIGNALLING. 337
if placed in the four-foot way, on account of the
small amount of space available. The bar, B, when
inclined for use, must project above the rail level ;
since the space between the rail is often filled up
at level crossings, the swinging rectangle must
necessarily be set high enough to miss all such
points. On the other hand, the bar must not
be of such a height as to come in contact with
the engine firebox, or any of the mechanism. Of
course, it is possible to place such apparatus on the
outside of the rails, but as engines do not always run
engine first, it would be necessary to provide bars on
both sides of each line of rail, or as an alternative
provide attachments on each side of the engine.
A similar apparatus, patented by Messrs. Raven
and Baister, of Darlington, is at present under trial
on the North-Eastern Railway Company's lines.
This arrangement is shown by Figs. 128 and 129.
The main principle is the operation of a special
alarm on the engine, when the latter is approaching
or passing a signal at danger. In this form, however,
the alarm takes the form of a special whistle, which
may be operated by steam or compressed air. The
valve controlling admission of steam or air to the
whistle is operated by the movement of the pendulum
levers, 6, when the latter come in contact with the
raised obstructions. The lever, L, which is connected
to the pendulum levers, carries a pin which works
in the straight slot, c1, formed on the lower end of
the rod, c, and also works in the curved slot formed
on the fixed plate, g. Movement of the pendulum, /?,
causes the pin to rise in the fixed curved slot, and
22
338
RAILWAY SIGNALLING.
raises cl and c, and opens the valve. It will be
interesting to note the progress made in this develop-
ment of automatic signalling, as, from the remarks
made, the necessity for some such method is
FIG. 128.
increasing. One of the greatest advantages arising
from the use of such methods as those just described
is due to the fact that they are in continual use,
RAILWAY SIGNALLING.
339
and, therefore, require no special arrangements to
be made, and involve no additional operations on
the part of any person concerned, to contribute
towards the results desired.
FIG. 129.
Such methods of signalling as are indicated by
Figs. 126-129 are capable of much more general use
than as mere substitutes for another form during
22
340 RAILWAY SIGNALLING.
exceptional circumstances. Whilst the general adop-
tion of such substitutes for the present outdoor
mechanical signals would constitute a revolution in
the method of signalling to drivers of trains, it
would, in the author's opinion, be a considerable
advance towards complete efficiency, and could not
fail to be more economical than the present methods
of signalling.
Closely connected with this part of the subject
is the question of repeating the positions of the
mechanical signals in the cabins from which they
are operated. The relative importance of the " on '*
and "off" indications has already been referred to.
It only remains to point out that confining repetition
to " distant " signals which are out of sight of the
signalman is not consistent. The general rule is to
repeat a signal which, even under normal conditions,
is not visible to the signalman ; and as " distant "
signals are more frequently out of sight than any
other, repetition is confined almost solely to this
class of signal. Bearing in mind the real reason
for repetition, it follows that any signal which
may, under any circumstances, be out of sight of the
signalman should be similarly treated. Very slight
consideration is necessary to show the advisability of
repeating all signals ; during fogr or snowstorms,
distant signals, which under normal conditions are in
plain sight, are quite invisible, as also are "advance"
and "home" signals in particularly bad cases. As
fogmen depend entirely upon the position of the
signal arm for their guidance, it becomes of double
importance that the signalman should have an
RAILWAY SIGNALLING. 341
accurate knowledge of their positions under these
circumstances. For these and similar reasons, the
increased use of repeaters of the positions of the
mechanical signal arms seems desirable ; and, as
already pointed out, the repetition should be that
of the arm itself, and not that of some point on
apparatus more or less intimately connected with
the arm.
Another point of great importance may be shortly
referred to. This is the need for an uniform system.
At present nearly every railway company's system
differs from those of other companies, in either the
regulations, or the apparatus employed, or both. For
this diversity of method, or apparatus, no really valid
reasons can be alleged. The handling of railway
traffic is practically the same wherever carried on,
and the fact that block working, wherever used, is,
in its essential characteristic — the enforcement of
a space limit — uniform, is proof that uniformity of
means to the end is merely a matter of arrangement.
The end in view in all cases is exactly the same,
and there is no reason to suppose that, generally,
any one of the ways taken is speedier or smoother
than the others. On the other hand, the advantages
accruing from uniformity of code and apparatus would
be considerable, and would put into the hands of
railway companies powers which, under certain con-
ditions, would be of the greatest importance, but
which they do not yet appear to appreciate. Unfor-
tunately, the amount of capital already invested in
existing apparatus precludes the idea of a speedy
reformation in this respect.
342 RAILWAY SIGNALLING.
It may be thought that in giving so much attention
to non-electrical methods, such as traffic arrangements
and the mechanical signalling of trains, the writer has,
to use a familiar colloquialism, " got off the rails."
The term " block system " is too frequently used to
indicate the electrical portion of the apparatus only.
It cannot, however, be too strongly emphasised that
the signalling which acts in notification of the move-
ments of the trains, and only indirectly controls those
movements, and that through another medium, is not
the whole of the " block system." The term " block
system," as the writer understands it, has a much
broader significance, and consists in the preservation
of a space limit between the successive trains; the
means used to effect this desirable end being of
importance only in proportion to the degree of
perfection attained in producing that effect. The
recognition of the necessity for a space limit is as
old as railways themselves, and the methods of the
present period are simply developments, rendered
necessary by continual increase of traffic, along a
line which has been rigidly marked out by a con-
tinual process of trial and error. In just the same
way that the weakest link must be taken into
account in gauging the strength of a chain, the
whole of the apparatus connected with the working
of traffic must be passed under review, before its
combined efficiency can be fully estimated. No
part can stand alone, Careful traffic arrangement
is necessary to ensure that smooth and speedy
working which is the first essential of all successful
work. Electrical signalling is necessary for the pre-
RAILWAY SIGNALLING. 343
iliminary arrangements required to marshal traffic
in the order of its importance, to facilitate its
passage with safety, and to notify its progress.
Mechanical signalling is the executive of both.
CHAPTER VII.
MR. ALEXANDER SIEMENS'S AUTOMATIC BLOCK
SIGNALLING SYSTEM.
From "Engineering."
In this system the trains automatically make
electrical contact at certain points along the line,
and the apparatus used by Mr. Siemens for this pur-
pose is shown by Figs. 130-135. In this system
powerful currents of electricity are necessary. In the
case of electric railways, the current would be taken
direct from the main conductor, and in other cases
either a special dynamo would be put down or the
current taken from the mains of an electric supply
company.
The signals are so arranged that they are set by the
passage of trains over certain portions of the line,,
and sets of such signals, applied to successive block
sections of the line, constitute an automatic system
requiring no attendants for working them. For this
purpose, at or near each end of a block section of
the line, a signalling apparatus is provided of the
following description.
On a horizontal axis is fixed a semaphore arm or a
set of coloured glasses, or both, these being counter-
weighted by a heavy arm on the axis, so that when
the axis is free the signals are moved by the counter-
weight to the position signalling " danger." The
RAILWAY SIGNALLING. 345-
heavy arm is a bar of iron bent to the form of a
circular arc, and arranged so that it can enter a.
solenoid coil. When this solenoid is excited by a
current of electricity the bar is attracted into it,
and the axis is turned, moving the signal arm to the
position indicating " line clear."
The signal arm axis carries another arm which,
in each of its two positions makes a contact, and in
one of the positions, corresponding to the " line clear"
position of the arm, this arm is held by a catch on
the armature of an electromagnet. The coils of this
electromagnet are connected with the contact maker,
Fig. 134, arranged at a certain part of the line at the
entrance to a block section, so that when a train
passes over the contact maker or rail treadle a current
of electricity is transmitted to the electromagnet,,
and the core being thus excited attracts its armature,,
withdrawing the catch from the arm of the signal
axis, whereupon the signal, in obedience to the
counterweight, assumes the "danger" position. At
the same time the arm, released from the catch,
moves away, breaking the contact for the electro-
magnet, and making a contact whereby a current is
transmitted to the next signalling apparatus behind,,
and this current exciting the solenoid there, causes
the signal to take the "line clear" position. On the
train reaching the next contact apparatus a like action
is repeated, the train thus automatically blocking
each section that it enters, and not unblocking it
until it enters the next section in advance.
From the description it is apparent that the signal
at the entrance to any one section cannot be made
346
RAILWAY SIGNALLING.
to indicate " line clear " unless the signal at the
entrance to the next section in advance has previously
been put into the " danger " position.
Although the control of one signal by another is
only described for the simplest case, it is obvious
that the electrical connections of three or more
signals can be so combined that each signal can
only be set to show " line clear " when certain other
signals are at "danger."
FIG. 130.
Figs. 130 and 131 are vertical sections on planes
•at right angles to each other of Mr. Siemens's
signalling apparatus. A is the axis on which is
fixed the semaphore arm or pair of coloured glasses,
•counterweighted by the bent iron bar, B, which
enters the heart of the solenoid, C, and is of
sufficient weight to hold the signal arm in the
•" danger " position. E is the electromagnet, the
RAILWAY SIGNALLING.
347
•spring armature, F, of which terminates in a catch
which holds an arm, D, fixed on the axis A. The
arm D, or it might be another arm fixed on the
axis A, is arranged to act as a switch making and
breaking contacts for the conductors to the solenoid
and the electromagnet in the following manner :
Assuming that a train is running along a section
•of line from X station to Y station, that the signal
.at X is at " danger," blocking the section against
FIG. 131.
the entrance of another train, and that the signal
at Y is at "line clear," showing that the train may
enter the next section from Y to Z, in that case the
apparatus at X has its bar, B, and arm, D, in
the position indicated by the dotted lines B1 and
D1, Fig. 130, but the apparatus at Y has the bar
B within the solenoid and the arm D held by
-the catch of F. As the train leaves the section X
RAILWAY SIGNALLING.
to Y and enters the section Y to Z, it, by acting
upon the rail treadle, causes the current to pass
through the coil of the electromagnet, E, at station
Y. The armature, F, being thus attracted, the
catch holding D is withdrawn, and the bar B
assumes the dotted position B1, the signal at Y
being thus set to " danger," blocking the section
Y to Z. At the same time D, in moving to the
position D1, breaks the contact for the electro-
magnet, E, and makes another contact whereby a
current is transmitted to the solenoid C at station
X. The solenoid then attracts the bar B, setting
the signal arm to " line clear," indicating that the
section X to Y is clear, and the signal at X is
retained at "line clear" by the catch F holding
D until it is released by a succeeding train entering
the section X to Y.
It is obvious that two or more signals as above
described may be combined in such manner that
two or more signals require to be brought into
the "danger" position before another signal can
be brought into the "line clear" position.
Such combination of signals is effected by the
employment of an . auxiliary signal apparatus or
relay constructed and operating as follows : Referring
to Fig. 132 two solenoids are arranged in combina-
tion with one iron core in such manner that when
a current passes through one solenoid so as to
attract the core, the latter remains in this position
even after the solenoid ceases to be excited, until
the second solenoid is excited, when the core will
be moved thereby into a second position, in which
RAILWAY SIGNALLING. 34Q
it at the same time breaks the circuit of such second
solenoid.
In the first-named position of the core it effects
the closing of a local circuit, which starts from a
contact made by a train when about to enter the
section protected by the signal, thence passes through
certain other conflicting signals, provided they are
in the " danger " position in which they make the
requisite contacts, then through the second above-
mentioned solenoid and into the signal of this
apparatus, effecting the lowering of the same to
"line clear."
The effect of employing the auxiliary signal
apparatus or relay is therefore that the signal in
connection with it is only lowered when the train
is about to enter the section, and when all con-
flicting signals are at " danger."
When applying this apparatus at a junction the
" entering " contact is not actuated by the train
depressing a rail, but several such contacts are
provided, each corresponding with one of the lines
of rails diverging at a junction, the one or other of
which is actuated by suitable means, according to
the destination of the approaching train. The
contacts may, for instance, be effected by permanent
projections on the engines when each engine has
always to go to the same destination, or they may
be effected by levers under the control of the engine
driver, so that he can select the line of the junction
along which he wishes to run his train by effecting
the particular contact by means of the corresponding
lever.
350
RAILWAY SIGNALLING.
The signals at a junction may be worked in con-
junction with the levers moving the points, so that
the electric current is made to move over the points
before the signal is lowered, or, in cases where the
levers are worked by hand, the electric signals
may be interlocked with them in any well-known
manner.
Fig. 132 is a section of the casing containing an
auxiliary signalling apparatus or relay, shown partly
FIG. 132.
in section. On an axis, A, is pivoted an arm, Br
carrying a semicircular bar, C, of soft iron. On the
base, D, are fixed the two solenoids, E and F, inta
the hollow interiors of which the ends of the bar, C,
enter, and in which they can freely move. On the
axis, A, is fixed a rotary switch or commutator, G,
against which bear springs, H K, the periphery
against which they bear being partly of conducting
material and partly of non-conducting material, so
RAILWAY SIGNALLING. 351
that contacts with the springs are made or broken
according to the position of the bar C. On the
axis, A, there may be several sets of commutators, G,
and springs, such as H K, according to the condi-
tions of the signalling circuits to which the relay is
applied.
When one of the solenoids, E for instance, is
excited by an electric current passing through its
coil, the one end of the bar, C, is attracted as a
core into it, and as in this movement its centre of
gravity passes the vertical line of its axis, it remains,
like a trembling weight, in the position to which it
is attracted after the solenoid, E, ceases to be excited.
But when the other solenoid, F, is excited, the other
end of the bar, C, is attracted into it, and the
bar tumbles to the other side, and remains there
after F ceases to be excited, until E is excited
again.
The current of each of the two solenoids, E and F,
is arranged in connection with the commutator, G,
and springs, H K, in such a manner that when
the bar, C, is made to tumble over to either side,
the circuit of the solenoid which it attracted is
opened, and the circuit of the other solenoid is
closed, ready to act when a current is transmitted
through it.
Fig. 133 shows diagrammatically the signals, con-
tacts, and connections at a junction, J, where S1? S2,
etc., are signals, as shown in Figs. 130 and 131, and
R! and R2 are relays, as shown in Fig. 132. In
the diagram the following conventional signs are
used :
352 RAILWAY SIGNALLING.
j. Contact made by signal being put to
"T^ " danger."
Contact made by signal being put to
" line clear."
This contact sets the signal in question to
" danger."
I This contact on post puts the signal to
" line clear."
TO Contact on rail to set signal behind train
to " danger."
Contact on rail to lower signal in front of
train, on condition that relay circuit
has been closed and all conflicting
signals are at danger.
The following examples may help to make the
diagram clear. Consider an "Up" main train to
make contact eb. This sets the signal, Slf to "danger,"
and puts the signal further behind to "line clear."
The train now passes on to contact fv and this will
set the signal, S^ to " line clear " if two conditions
are fulfilled, (i) That a previous " up " main or
branch train has passed over contact e$, thereby
pulling over the relay R1? thus closing contacts 2 and
3, and breaking contact I. (2) That the conflicting
signal S4 is at " danger." If either of these con-
ditions is not fulfilled the train cannot lower the
signal S2, and the driver must pull up and wait on
contact /2 until the relay contacts 2 and 3 are closed,
and the signal S4 is put to " danger." This ensures
that a previous " up " train must have passed the
RAILWAY SIGNALLING.
353
contact £6, for the signal S4 can only be put to
" danger " by a train making contact e7, and the
FIG. 133.
•relay Rx can only be pulled over by the same train
making e6. Under these conditions a current can
23
354 RAILWAY SIGNALLING.
flow from /2 through S2 (lowering same), through
contact a4 on S4, through contact 2 on relay R: to
common return. As soon as S2 is lowered the contact
62 is made, and the current then passes through
contact 3 of relay R1? through solenoid to common
return, thus making i and breaking 2 and 3 of the
relay. Having lowered S2, the train can now pass on
to £7, the making of which has the effect of pulling
S2 to " danger," and Sj to " line clear." Passing on
further, the contact eQ is made, and the signal S3 is
put to " danger," also the relay Rx is pulled over,
breaking contact I and making 2 and 3. Everything
is now ready for the next main or branch " up " train
that comes along. If it is a branch " up " train a
similar series of contacts are made. For, on making
/3, a current can pass through S6 if it is at " danger, "
through S2 if at " danger," through S4 (lowering
same), through 2 of relay Rx to common return.
This ensures that no main " up " train can get past /2,
that no main " down " train can get past S6, also the
previous "up" train has passed e6. Passing on to
£7, the signal S4 is put to " danger," and S7 is put
to "line clear."
Next consider a "down" main train leaving the
junction, J, having made contact glt by a lever or
other device, on the locomotive. This will lower S6 on
condition that the signals S4 and S5 are at " danger,"
and that the relay R2 has been pulled over (thus
closing contacts 5 and 6) by either a previous " down "
main train having passed over 02, or a previous
" down " branch train having made 04. If these con-
ditions are not fulfilled the train must wait on g2 until
RAILWAY SIGNALLING. 355
the preceding train, if it was a " down " branch train,
has passed 03, putting S5 to "danger" and S8 to "line
clear," and has further passed e4, pulling over relay
R2, thereby making contacts 5 and 6, and at the same
time putting S9 to "danger"; or until the preceding
train, if it was a "down" main train, has passed el9
pulling S6 to "danger" and S8 to " line clear," and has
passed £2, putting S10 to " danger," and at the same
time pulling over relay R2, making contacts 5 and 6.
Under these conditions a current can pass from g2,
through S4, through S5, through S6, thereby lowering
same, through contact 5 of relay R2 to common
return. The lowering of S6 makes the contact b6,
thereby allowing the current to pass through con-
tact 6 and round solenoid of R2 to common return,
thereby pulling over core of R2, making contact 4,
and breaking contacts 5 and 6 ready for the same
train, when it passes ev to send a current through 4
of R2, round solenoid to common return, making 5
and 6 and breaking 4.
If the next train leaving the junction, J, is a
branch train, a similar series of contacts are made.
For on making hlt if all is safe to proceed — that is,
if S6 has been put to " danger " and the contacts
5 and 6 of relay R2 have been made — a current
can pass from /^ or H2 through S6, through S5,
lowering same, and through 5 of R2 to common
return. On lowering S5 contact b- is made, and
the current passes through 6 of R2, through solenoid
to common return, thus pulling over core of R2,
making contact 4, and breaking 5 and 6 ready for
the same train, when it has reached e±, to pull back
23*
356
RAILWAY SIGNALLING.
the core of R2, making contacts 5 and 6, and
breaking 4. On passing e5, the signal, S5, is put to
" danger."
In the foregoing description the automatic actua-
tion of the points by the trains themselves has not
been mentioned. It only remains to show how the
trains automatically change over the points in order
to complete the description of this system. Fig. 134
shows an arrangement of an electric motor and
connections for actuating the points, and Fig. 135
is a diagram which shows how the contacts of
Fig. 134 are connected to the system itself.
FIG. 134.
Referring now to Fig. 134, the movable rails or
points are fixed to a rod, D, which extends beyond
the rails and has fixed into it a pin, p, which
engages with a lever, L, pivoted at x. An iron
disc, F, turns about x as centre, and has fixed
near its edge a weight, W, and the two pins, g
and h, which are long enough to strike the lever,
L, when F is turned round. A spur wheel, H, on
the other side of F turns about x as centre, is in
gear with a pinion on the motor shaft, and carries
RAILWAY SIGNALLING. 357
a pin which is capable of engaging two projections
on the disc, F. Insulated from the rod, D, and
moving with it are three metal strips, rlf r2, rB,
which, when the rod, D, is in its extreme position
on the one side, connect contact pieces, a^ bv a2 b2,
as 63, respectively, and in the other extreme position
of the rod connect bt clt b2 c2, 63 c3, respectively.
The contacts a3, b&, c3, are for reversing the current
through the motor armature, at the same time
keeping the direction of the current in the field-
magnet coils the same. The contacts, a^ b-± clt
a2 b2 c2, a3 bz CB, are shown in Fig. 135 in connec-
tion with the relay R2 and signals, and will be
referred to presently. Suppose the rails to be in
the position shown in the figure — that is, a^ b19
a2 b2, a3 63, are respectively connected. If a current
flows to bi from an outside source, it passes via the
strip ;'j to the contact alf from thence through the
armature of the motor, through «8, via r% to 63,
through the electromagnet winding to the common
return. This causes the armature to turn in the
direction of the arrow, and the spur wheel, H, is
turned until its pin comes in contact with the
projection on the disc, F, thereby turning the latter
round and raising the weight, W. As soon as W
gets past the vertical position it falls, and the pin, h,
striking against L carries it with it, thus moving
over the points, and making contacts bl clf 62 c2,
bB c3. At the same time the current through the
motor is broken.
If a current flows from an outside source to 62,
when the rails are in such position that bt clf b2 c2,
358
RAILWAY SIGNALLING.
b3 c3 are connected, the current through the armature
of the motor is in a reverse direction, and the rails
are automatically put over to the other side.
In Fig. 135 actual connections, contacts, etc., are
FIG. 135.
given in the case of signals S5 and SG. Reference
is made to Fig. 133 for the relative positions of the
rails themselves with respect to the signals, rail
treadles, etc., shown in Fig. 135. The following
RAILWAY SIGNALLING. 359
explanation is given in order to show how the points
are automatically changed over by the train itself,
and the subsequent operation of the signal in
question.
Consider a main "down" train (Fig. 133) having
made gl or g%. If the signals S4 and S5 are at
" danger," a current can pass to 6t. If the points
are not yet right, contact is made between 6j alt
b2 a2, and 63 aB respectively, and the current passes
through the motor, causing it to put over the points,
as already described. Contacts ^ clf b.2 c2, 63 c3 are
now made, and the current is thereby diverted, and
now passes via C through the solenoid i6 of the
signal S6, thereby lowering the same on condition
that the previous " down " main train has passed
over 04, putting S10 to " danger," and also closed
contact 5 of relay R2; or a previous branch "down"
train has passed over *4, putting S9 to " danger," and
also closed contact 5 of relay R2. Having lowered
S6 the driver can proceed, knowing that his points
are right, that S4 and S5 are at danger, and that
the previous " down " main or branch trains have
passed e.2 and £4 respectively. On lowering S6 the
contact b$ is made, and the current finally passes
through the solenoid, », and the contact 6 of R2,
breaking contacts 5 and 6, and making contact 4.
On arriving at elf a current passes through contact
K5 of S5, for it is at " danger " ; through mCj and
electromagnet, M6, of signal S6, thereby putting the
same to " danger," and the current passing through
contact 4 and solenoid, p, of relay R2, puts over same,
making contacts 5 and 6, and breaking contact 4.
360 RAILWAY SIGNALLING.
If the train is a "down" branch train, a similar
series of contacts are made. For on making Jil and
7&2, if S6 is at " danger," a current can pass to 62r
and will change over the points, as already described,
thus automatically making a2 Z>2. It is then diverted
and passes via a2 through solenoid, i5, of S5, lowering
same on condition that a previous " down " main
train has passed over e2) putting S10 to " danger,"
and also closed contact 5 of relay R2 ; or a previous
branch " down " train has passed over 04, putting
S9 to " danger," and also closed contact 5 of R2.
Having lowered S5, the driver can proceed, knowing
that his points are right, that S6 is at " danger,"
and that the previous " down " main or branch
trains have passed e2 and e± respectively. On lower-
ing S5 the contact b- is made, and the current
finally passes through the solenoid, n, and contact 6
of R2, breaking contacts 5 and 6, and making
contact 4.
On arriving at e3 a current passes through contact
m5 of S5, for it is at the " line clear " position,
through electromagnet, M5, putting S5 to " danger,"
and having thus made K5, it passes via KG to signal
Ss, and lowers same. It is now impossible for
another branch " down " train to lower S5 until the
train in question has passed £4 ; and this it cannot
do until the train in front of it has lowered S&J,
thereby opening the section. On arriving at
£4, signal S9 is put to " danger," and the
current passing through contact 4 of R2 puts
over same, making contacts 5 and 6 and breaking
contact 4.
RAILWAY SIGNALLING. 361
TIMMIS'S AUTOMATIC SIGNALLING SYSTEM,
LIVERPOOL OVERHEAD RAILWAY.
One of the most interesting applications of electrical
traction is that of the Liverpool Overhead Electric
Railway, the success of which is gratifying evidence
of the applicability of electricity to railway working
under suitable conditions. Not the least interesting
part of the enterprise is the electrical signalling, which
is automatic throughout the line. The arrangements
for this purpose are all to the design of Mr. J. A.
Timmis, to whom the author is indebted for the
following description and illustrations.
As is well known, the line is used for passenger
traffic only, and the arrangements are of a cor-
respondingly simple character ; the deviations from
purely straight running lines consisting of one cross-
over road at each intermediate station, and two at
each terminal station.
The total length of the railway is nearly seven
miles, and it is now being extended. There are
thirteen stations, numbered from two to fourteen,,
and as the distance between successive stations
constitutes the block section, there are in all twelve
block sections.
The signal arrangements at intermediate stations
consist of a " home " signal, which stands at a
distance of about one hundred feet from the platform
end, behind the train standing there, and a "starting"
signal at a short distance in advance of the platform..
The latter signal, as will be seen later, acts also as a
" distant " signal for the station in advance. At the
362
RAILWAY SIGNALLING.
terminal stations of the line an " advance starter "
is added to the signals already described. All these
signals are operated electrically by means of suitably-
placed contacts, which in certain cases complete, and
FIG. 136.
in other places break, circuits operating the signals
as may be required.
The form of signal used is shown by Fig. 136. The
contacts made or broken, as the case may be, by the
passage of trains are each operated by a long arm
RAILWAY SIGNALLING. 363
standing by the side of the rails, which projects into
the path of a bar carried on the last vehicle of each
train. The arm is moved through an angle of forty-
five degrees, and held there during the time taken by
the train operating it to move through a distance of
twenty-four feet. The contact surfaces are long, and
move over each other with considerable friction in
order that they may be kept perfectly clean.
The signal arms are worked by electromagnets
specially designed by Mr. Timmis for the work. An
electromagnet measuring seven inches by five inches
in diameter will raise a weight of fifty-six pounds from
a distance of two inches when a current of five
amperes is passed through the coil. When used to
operate a signal the load is much less than this, and
when the signal has been lowered the current required
to maintain it in that position is, of course, much less
than that required for the initial effort. For this
reason the operation of lowering the signal arm is
made to bring into the circuit a considerable resistance
which reduces the current from five amperes to about
one quarter ampere. Even this current is large for
the maintenance of the signal arm in the "off"
position, since one-tenth of an ampere has been found
experimentally to be quite sufficient. A very large
margin is thus allowed over the actual requirements.
All signals are fitted with a switch working in
connection with the electromagnet operating the signal
arm. In the " off" position of the signal arm the
switch makes such contacts as passes a " holding
down " current from the battery at the local station ;
position the switch is
364 RAILWAY SIGNALLING.
in such a position as to pass a "lowering" current
through the coils of the electromagnet from the
advance station, the resistance being cut out.
Separate line wires are run for each line of rails..
These line wires commence at the " starter " signal at
one station and run to the "starter" signal at the
next station in advance, connecting with the inter-
mediate "home" signal en route.
The " starter " signals at intermediate stations are
fitted with mercury contacts by which the line wire
for that section may be completed or broken in
accordance with the position of the arm. Two plates,,
which form the connections, are fixed within a vessel
containing mercury, which is attached to the arm of
the signal. When the arm is in the "on" position, the
mercury connects the two plates and completes the
circuit of the line wire ; when in the "off" position,,
the mercury flows away from the plates and leaves
them insulated from each other, arid thus breaks the
circuit of the line wire. It should be noted that the
connection between the plates is never broken by the
mercury flowing away from them when a current is
passing.
All " home " signals are fitted with a mechanical
lock, which is maintained in its inoperative position
by a key which is hung upon it. At one time this key
was used to unlock the lever of the cross-over road
points. Its removal from the mechanical lock set
that " home" signal to " danger " irrespective of the
action of the electromagnet, and without interference
with the latter. This arrangement has now been
superseded by a device by which the cross-over road
RAILWAY SIGNALLING. 365
lever is locked in position by two bolts which are
themselves held in the locking position by an electro-
magnet actuated by the " holding down " currents
of the "up" and "down" "home" signals
respectively.
Fig. 137 represents diagrammatically the connec-
tions making and breaking contacts, signal operating
electromagnets, and two-way switch in connection
with the resistance, the " starter " signal mercury
contacts, " down " platform switches, mechanical
locks and batteries, etc., for normal working at three
stations at each end of the line. If we assume that a
train is about to travel on the " up " line between
No. 2 and No. 3 stations and follow its course, the
arrangements for ensuring safety will became apparent.
If we further assume that no train is in the section
between No. 2 and No. 3 station all signals will be
" off."
Contacts A, B, and D (Fig. 137) are breaking con-
tacts, E is a making contact. " The " advance
starter" signal at No. 2 station is maintained in the
"off" position by the contact A, the electromagnet,
resistance, and contact 2 of the switch. The " home "
and " starter " signals at No. 3 station are maintained
in the same position by similar currents passing
through B and D respectively from the battery at
No. 3 station. Another circuit is formed at No. 3
station from the battery through E, the mercury
contact on the " starter," and by the line wire to the
" home " signal at No. 3, and the " advance starter "
at No. 2. This circuit is broken at two points — viz.,
at E, which is a making contact, and at the mercury
366
RAILWAY SIGNALLING.
ii
RAILWAY SIGNALLING. 367
contacts on the arm of the " starter " signal at
No. 3 station.
Referring to Fig. 137, we find that the passage of
the train past A breaks the circuit at that point, and
cuts off the " holding down " current during the
time the train actuates A. The " advance starter,"
therefore, goes to " danger," and this operation
involves change of the switch on the signal such
that contact points 2 and 4 become connected. The
contact A is remade as soon as the train passes that
point, but the "advance starter" signal arm is not
lowered, since the circuit previously existing from
the battery at No. 2 station is broken by the fresh
position taken up by the switch. In any case the
current set up by the battery at No. 2 station is not
sufficiently strong to give the requisite pull to lower
the signal, as it necessarily passes through the
resistance.
Following the train on its passage to No. 3 station,
we find that on approaching the "home" signal for
that station, which is " off," the contact B is
broken and the signal put to " danger," whilst the
switch contacts are rearranged precisely as described
in connection with the " advance starter " at No. 2
station. In order to ensure the " home " signal
being put to "danger" by the train, the contact B
is double, and operation of either will release the
signal arm. If one contact fails there is still another
to be relied upon, and it is extremely unlikely that
both would fail together. It will be noticed that
there are two signals now standing at " danger " behind
the train, the progress of which has, so far, been traced.
368 RAILWAY SIGNALLING.
After stopping at the platform, the train proceeds
towards No. 4 station. The "starter" of No. 3 is
still "off," but, on the train passing the contact D,
this signal is put to " danger " in precisely the same
way, and with the same effect upon the switch working
in connection with the electromagnet, as in previous
cases. Moreover, the putting of the " starter " of
No. 3 to " danger," closes the circuit of the " up "
line wire through the mercury contact on the arm of
the signal. There are now three signals at " danger "
behind the train.
When the train passes forward to E, it operates the
making contact at that point, and the " starter " signal
arm of No. 3 station being at " danger," a current
passes from the battery of No. 3, through the mercury
contacts of the starter, along the " up " line wire to
the " home " signal of No. 3, where it divides, part
passing through the " home " signal circuit, and part
passing to the circuit through the "advance starter"
at No. 2. Remembering that the signal switches of
these two signals are connecting contacts 2 and 4.
we see that the current set up by the making of the
contact E will be of sufficient strength to lower the
signal arms, since it does not pass through the resist-
ance in connection with the switch of either signal.
The result is to place the " home " at No. 3 station
and the " advance starter " at No. 2 station in the
"off" position, and to replace the switches of these
signals in their original position. The current set up
by the closing of E lasts for a comparatively short
time only, but a glance at the diagram will show
that the work of maintaining the two signals in the
RAILWAY SIGNALLING. 369
'"off" position is taken up by the battery at No. 2
for the " advance starter " there, and through another
circuit from the battery at No. 3 for the " home "
signal at that station.
It will be noticed that the " starter " signal of
No. 3 station is still at "danger"; and, further, by
the arrangement of the mercury contact with the
line wire circuit and contact E, it is absolutely
necessary for this signal arm to be in that position
before the passage of the train past E can operate
to replace the two signals in the rear.
If we follow the train during its further passage in
the same direction, we find that the "starter" at
No. 3 station is maintained in the "danger " position,
until the " starter " at No. 4 station is placed in that
position by the operation of the making contact,
corresponding to E at No. 3 station, at that place ;
the operation of the " home " signal at No. 4 station,
meanwhile, being precisely as described for No. 3 station.
Hence, we see that a train starting from any
station is protected by one signal being at "danger"
until it reaches the " home " signal at the advance
station ; whilst standing at the platform of any inter-
mediate station it is protected by two signals ; and
for the short distance between the contacts D and E
it is protected by three signals standing at " danger."
It will be noticed that placing the third signal to
" danger " behind the train is not intended as an
additional protection for the train, but is necessary
to ensure that that signal is protecting the train,
before the other signals in the rear are lowered
for the passage of a succeeding train.
24
370 RAILWAY SIGNALLING.
The operations at all the intermediate stations are
precisely the same, and it is not therefore necessary
to follow the passage of the train further. The
arrangement ensures, so long as the signals exhibited
are observed, that the space between successive trains
is that between successive " starters " so long as we
consider the continuous passage of trains in one
direction from one terminal station to the other.
One point in connection with the design of the
apparatus may be here noted. The signal arms are
held in the "off" position by a continuous current
only ; their position when not under constraint is at
" on." Hence any failure of the circuits which causes
interruption of the current acting upon the signal arm
has an effect which stops the passage of traffic, and
therefore tends to safety. This is a most important
point, and is, of course, the practice on all railways;
the temptation to reverse the practice where the
signals are operated by electrical apparatus is, how-
ever, much greater than where mechanical appliances
are in use, on the ground that, as is the case at
Liverpool, the normal, and therefore the most
prolonged position, if maintained actively will be
more costly than if maintained passively or by
gravity.
The exigencies of railway working, however, demand
more than the simple straightaway running already
described, even for so favourable a case as the Liver-
pool Overhead Railway. Trains may require to
shunt from the " up " line to the " down " line, or
vice versa, in consequence of a breakdown in one of
the sections ; and, as has already been stated, cross-
RAILWAY SIGNALLING. 371
over roads are provided at each station for this
purpose, although their use is exceptional.
Suppose the train, the progress of which has been
traced between Nos. 2 and 4 stations, required, on its
arrival at No. 3, to return to No. 2, instead of passing
to No. 4. It will be remembered that the " advance
starter " at No. 2, and the " home " at No. 3, are
both at " danger " when the train is standing at
No. 3 station platform. The train will draw forward
to clear the cross-over road points ; but in doing so
will not actuate the contact D or E, the distance
between the points and D being sufficiently great to
allow of any train standing between them without
operating the latter. Hence, the "up starter" at
No. 3 station is not placed to "danger," and the
"up" line is protected by two signals in that
position in the rear of the train.
Assuming that the arrangement for effecting the
shunt are the keys by which the lever of the cross-
over road points are released, we find that removal
of the keys sets the "up" and "down" "home"
signals at " danger/' and provides that they shall not
be operated in the usual way during the time the
keys are in use. The levers are thus blocked, and
there is no danger that the " home " signals will be
lowered during the time occupied by the shunt.
When the points' lever is released the cross-over
road is set by hand, and the movement of the lever
results in the switch, S, forming the local battery
with the two contacts F and G.
The passage of the train over G sets up a current
which passes to the " up " line wire, and thence
24*
372 RAILWAY SIGNALLING.
through the electromagnets at the " home " signal
at No. 3 and the " advance starter " at No. 2. The
latter signal is placed in the " off" position ; the elec-
tromagnet of the former is operated and the switch
changed, but the arm is not lowered owing to the
action of the mechanical lock.
Hence, the " up " line is still protected by the
" home " signal standing at " danger."
The passage of the train over F does not affect
that contact, since F and G are only actuated by
trains passing from the " down " to the " up," and
from the " up " to the " down " line respectively.
The further passage of the train over H places
the " down " line starter to " danger." If the keys
are now replaced upon the " home " signals, the
latter will be replaced to "off," but the train will be
protected by the " starter." The passage of the train
over the contact P at No. 2 station places the starter
at No. 3 in the " off" position. This completes the
cycle of operations required to work a train through
any of the cross-over roads provided at intermediate
stations.
If we carefully consider the arrangements described
and the effects produced in their proper order, we
shall be able to estimate more accurately the degree
of safety secured by the use of the apparatus as
shown by Fig. 137, and thus be in a position to
contrast it with that secured under the usual con-
ditions of signalling, both as regards the running
between stations, and for shunting operations such
as have just been considered.
The train arrives at the point from which the set
RAILWAY SIGNALLING. 373
back is to be made with two signals at "danger"
behind it — viz., the " advance starter " at No. 2
station, and the " home " at No. 3. The "starter"
at No. 3 remains " off," since the train does not
require to actuate the breaking treadle, D, in order
to allow the cross-over road to be set for the train
to pass to the " down " line. Removing the key
for the points' lock from the " up " " home " signal
brings into play a further protective device, which
prevents that signal arm being placed to " danger "
by the usual means, although the movements which
usually have this result may be made.
Turning to the " down " line, the signals for trains
approaching No. 3 from No. 4 have to be considered
before the operation of shunting is actually com-
menced. A little consideration will show that the
" home " signal, under normal circumstances, is only
at " danger " for the time the line between the
contacts I and K is occupied. Under such circum-
stances, the shunt from the " up " to the " down "
line could not be made. Assume, then, that the
three signals — " down starter " at No. 4, " home "
and "down starter" at No. 3— are all in the "off"
position. The removal of the key from the "down"
" home " signal at No. 3, puts the arm to " danger."
The condition of the signals, etc., at this point in
the operations is shown by Fig. 138.
The passage of the shunting train over G leaves
the cross-over road protected by the "home" signal
of No. 3, and a train from No. 2, on the " up " line,
may proceed to that point. The " down starter " at
No. 4 station is "off" also, and a train may proceed
374
RAILWAY SIGNALLING.
1
i?3.
UpHome\
Up Starter
HO:
H°3
'« U Up Home
-Starter
-J=
wa
Up Starter
* £
Up Hot
N°2.
Up Advance
Starte,
1=
\\
RAILWAY SIGNALLING. 375
•on the " down " line to the " down " " home " signal
at No. 3. Neither of these trains will interfere with
the operation of the cross-over road. The condition
•of the signals at this stage is shown by Fig. 139.
The passage of the shunting train past H puts the
^' down starter" at No. 3 to "danger" behind it.
The replacement of the key on the "down" " home"
lowers that signal and allows the train standing there
to advance to the platform, the " home " signal being
put to " danger " by the operation of the contact I.
The passage of the shunting train past the contact K
will lower the " down starter " at No. 4, and the
•" down home " at No. 3. Hence, in order to ensure
protection for the train, which we have considered as
standing at the " down home " of No. 3, when it
.arrives at the platform, its passage over the contact I
should not be made until the shunting train has passed
K. Unless this condition is complied with, the pas-
sage of the shunting train over K would lower both
the " home " at No. 3 and the " starter " at No. 4,
if the latter is in the "on" position, and the train
standing at the platform (Fig. 140) will not be pro-
tected by any signals.
In so far as the train, which has been assumed to be
standing at the " up " " home " signal during part of
the operation of shunting (Fig. 139), is concerned, the
replacement of the points' lock key will lower the
arm and allow the train to proceed to the platform
{Fig. 140), the " home " signal being placed to
"danger" by the passage of the train over B. Its
further passage over D and E will result in the " up
.starter" at No. 3 being put to "danger," and the
RAILWAY SIGNALLING.
"up advance starter" at No. 2 and the "up home""
at No. 3 being lowered respectively.
As already stated, the arrangement by which the
cross-over road lever was unlocked by a key kept on
the " home " signal has been superseded by another
device, which is as follows :
The cross-over road lever is locked in its normal
position by two plugs. These plugs are themselves
locked in position by an electromagnet, actuated by
the holding currents of the " up " and " down "
" home " signals respectively. Thus, with both
" homes " at " off," both plugs are locked. On.
the "up" "home," say, being put to "danger" by
a train passing over the contact B into the station,,
the corresponding plug is pulled out, which breaks
the line - wire circuit to that " home " and the
" starter " in the rear. A similar movement is gone
through for the "down" road, and the "down" line
wire to the local "home" and the rear "starter"
is broken. The lever is then free to be worked on
the train clearing the cross-over road, and the roads
are both blocked in the rear. The key may be done
away with, or used in the case of an emergency.
On the shunting being completed the lever is put
back, but both roads are blocked. As this shunting
is in the nature of an exceptional circumstance, the
first train from either direction has to run " against
signals," which is provided for by a pilot or special
code on the station bells when normal working is
resumed.
The arrangement of the terminal station No. 2 is
shown by Fig. 140, and the terminal No. 14 by Fig. 141.
RAILWAY SIGNALLING. 377
At each of these stations there are two cross-over
roads. At No. 2 station a small cabin, containing a
five-lever frame, is situated on the "down " platform;
and at No. 14 station a similar cabin, with a four-lever
frame, is provided on the "up" platform. Sykes's
bars are used at three stations to control the signals
and points. The following table refers to station
No. 2, the connections for which are shown by
Fig. 140.
TABLE I. — Arrangements at No. 2 Station.
Train on bar No. i ....................... No. 9 signal up.
»> >» j» -WO. 2 ........................ ,, 7 »> >»
» » » No. 3 ................... — ••• »> 4 » »
,, off bar No. 3 ....................... ,, 4 ,, down and No. 5 up.
Train off bar No. 3, and points 6 \ No. 5 signal down and Nos. 4
closed for cross-overs .................. / and 7 signals up
Train off bar No. I ........................ No. 9 signal down and No. IO up,
Train off bar No. I, and points 8\ No. 10 signal down and No. 9-
closed for cross-over .................... / up.
Train off bar No. 2 ......................... No. 7 signal down.
Train off bar No. 2, and points 6^ XT „ • ol ,„
closed for cross-over. ......... _ _______ ) No' 7 S1^al UP'
The corresponding arrangements for No. 14 station
are given below.
TABLE II. — Arrangements at No. 14 Station.
Train on bar No. i ..... ................ No. 6 signal up.
„ „ „ No. 2 ...................... _ „ 7 „ „
„ ,, „ No. 3 .......... ___ ......... Nos. 8 and 9 signals up.
,, off bar No. 3 ........................ No. 8 signal down and No. 9 up.
Train off bar No. i ........................ No. 6 signal down and No. 7 up.
The estimate of the cost of the electrical energy
expended in working the signals is remarkably small,
37*
RAILWAY SIGNALLING.
UNIVERSITY
RAILWAY SIGNALLIN^^ii^^^ 379
Each station is provided with four signals, which, with
a three minutes' service of trains, will each be lowered
four hundred times during a working day of twenty
hours. If the lowering current of five amperes is on
for one second, the quantity used during the working
day is
40Q * * * 5 = -55 ampere-hours.
3,600
The electromotive force is forty volts, and the
expenditure of electrical energy per signal per day
for lowering purposes is, therefore, twenty-two watt-
hours, and for each station eighty-eight watt-hours.
This, however, does not include the holding-down
current. Assuming each signal to be down one and
a-half minutes, for each of the foregoing four hundred
movements it will be down six hundred minutes per
day. The current being one quarter ampere, the
quantity will be
—5- = 2*5 ampere-hours.
60
The expenditure of electrical energy for maintain-
ing the signals, at one station, "off," will be four
hundred watt-hours, and the total for both purposes
will be
watt-hours per station per day.
Taking this as the average for all thirteen stations,
the total expenditure of energy for the whole railway
works out
6*344 kilowatts per day ;
380 RAILWAY SIGNALLING.
which, at 8d. per kilowatt,
= 43. 2fd.
As evidence of the reliability of the electrical
apparatus for actuating signals, it may be said that,
on the Liverpool Overhead Railway, there has been
no failure of a signal to go to " danger " at the
proper time for over eighteen months, or no failure
in nine millions of workings.
TIMMIS'S ELECTRICAL APPARATUS, EARL'S COURT.
Mr. Timmis's work on the Liverpool Overhead
Railway is more particularly related to the actuation
of the outdoor signals exhibited for the guidance of
drivers than for signalling the passage of trains from
one point to the next in order on the line. Another
example of this gentleman's work in this direction
is shown by diagrams (Figs. 143-147), which represent
the arrangements in use at Earl's Court Station.
The apparatus includes electrical methods of
actuating points and locking bars and bolts, sema-
phore signals, and ground discs, and provides for the
electrical interlocking of the levers by which these
operations are, initially, brought about.
Fig. 143 is a diagram of the section of the line
where the apparatus is in use, and shows the signals
and points. Fig. 144 is a diagram of the wiring of
the installation, and shows the electric switches by
which the points, signals, and ground discs are
operated, the detectors, lock magnets, and lock
switches for carrying out the system. Fig. 145
shows details of the points actuating apparatus.
RAILWAY SIGNALLING.
381
RAILWAY SIGNALLING
RAILWAY SIGNALLING.
383
384
RAILWAY SIGNALLING.
Fig. 146 shows details of the electric lock switch,
and Fig. 147 shows the arrangement for actuating
the signals and ground discs.
As will be noted from Fig. 144, the points actuated
by electrical means are those for the double cross-
over roads, marked 36 36 and 37 37 ; the apparatus
TO DETECTOR
_ j
FROM LOCK
FIG. 146. — Connections for Electric Lock Switches, 11-20, 23, 24, 47-50.
shown by Fig. 145 being represented in Fig. 144,
-diagrammatically, by a a, b b. These points, it will
be seen, are operated in pairs, and an examination
of Fig. 145 will show that the current is only used
•during the operation of changing the position of the
points.
The semaphore signals 39 and 40, and the ground
RAILWAY SIGNALLING.
385
•discs 47-50, are actuated electrically, and are held
in the "off" position by a continuous current, as on
the Liverpool Overhead Railway ; the strength of
the current being reduced, after the initial effort of
lowering the signal arm, by the interpolation of a
.resistance in the circuit, as shown by Fig. 147.
CABIN
TO Ncc AT i vg
FIG. 147. — Connections for Signals and Ground Discs, 39, 40, 47-50.
The points 36-37 are actuated by the levers having
the same numbers ; and the signals 39 and 40, and
the ground discs 47-50, are each operated by the
similarly numbered lever. The operation of the
levers 11-24, controlling similarly numbered signals
'(Fig. 143), depends upon the position of the detectors.
25
386 RAILWAY SIGNALLING.
The levers are locked in the frame in the ordinary
way, in addition to the electrical control, and it is
thus impossible for a signal or ground disc to be
operated unless the points which it controls are
properly set and locked.
The cost of working such a system is said to be
remarkably low. Assuming that each pair of elec-
trically-actuated points is operated two hundred and
forty times per day, or once every six minutes, the
cost of the electrical energy used is put as less than
one farthing per pair of points per day. The cost
of operating the signals is stated to be less than one
halfpenny per signal per day.
Over and above the low cost of operating, the
advantages claimed for the system are its capability
of working signals, etc., safely at any distance from
the point of operation, and the possibility of dis-
pensing, in many cases, with intermediate cabins ;
the signals at such places as those at which inter-
mediate cabins would otherwise be necessary, being
operated from the advance or rear cabins as might
be desirable, the positions of the signals, etc., being
at all times repeated in those cabins.
The actuation of points and signals by electrical
means, as done by Mr. Timmis in the instances
given, and as suggested by Mr. Siemens, would
appear to open up a wide field for the employment
of electrical apparatus, and, combined with elec-
trical interlocking of the means of operation, would
undoubtedly tend to the benefit of the service by
decreasing the manual labour necessary for operating
the apparatus, and by economising space ; and would
RAILWAY SIGNALLING. 387
also, no doubt, decrease the initial cost of fitting up
the cabins.
There is, of course, no novelty in the suggestion
to interlock the means of operating signals, etc., by
electrical methods in preference to the mechanical
means now employed for the purpose, and which
have given such excellent results. Such methods
are of old standing — as suggestions — but have never
passed much beyond the experimental stage, prob-
ably owing to the fact that electrical apparatus was,
until recent years, constructed with a view to the
electrical effects intended, and without sufficient
consideration to the conditions under which it
would have to be used to produce mechanical effects
of any appreciable magnitude. The present time,
when it has been recognised that mechanical effort
is not efficiently transmitted through paper, paraffin,
wax, or silk, and is not assisted by the most liberal
use of varnish or lacquer, would seem to be oppor-
tune for a revival of the efforts to actuate points,
signals, and other apparatus, situated at a distance
from the point of operation, by electrical means,
and to interlock the means of operation by the
same agency.
25*
I 1ST ID IE IXI.
A.
" Absolute " Block 140
Acceptance of Train with
another at " Advance" Signal 176
Acknowledgment of Signals ... 50
Adjustment of S N Instrument
Dials on Account of Dis-
turbance 143
"Advance" Signals 116
Advantages of Block Signalling 24
Advantages of Single-Needle
Instruments 141
Analysis of Electrical Block
Signals 33
Applicability of Apparatus to
Obviate Accidents 329
Assistant Engine in Rear 55
Aural Outdoor Signals 109
Automatic Instruments 171
B.
Bains's Signalling Instrument... 137
Ballast Train Requiring to Stop
in Section 56
Bartholomew's Apparatus 8
Bell Signal Codes 34, 48
" Be Ready " Signal 44
Birmingham and Gloucester
Rail way Company's Signalling
by Telegraph 6
Blakey and O'Donnell's Appa-
ratus : Description 226-228
Blakey and O'Donnell's Appa-
ratus : Objects Attained... 235-238
Blakey and O'Donnell's Appa-
ratus : Objects of Design 229
Blakey and O'Donnell's Single-
Needle Block Apparatus 226
' ' Block," Application of Term
to Early Signalling 22
Block Indicators: Bartholomew's 76
Block Indicators : Cooke and
Wheatstone's 74
Block Indicators: Great
Northern Railway Early Form 74
Block Indicators : Hodgson's ... 86
Block Indicators : L. and N. W.
Ry. Co.'s Early Double-
Needle Form 75
Block Indicators : Preece's Early
Form 77
Block Indicators : Preece's Later
Form 85
Block Indicators : Regnault's... 75
Block Indicators : Single-Needle 83
Block Indicators : Spagnoletti's 84
Block Indicators : Tyer's 85
Block Indicators : Tyer's Early
Form 75
Block Indicators : Uses of 73
Block Indicators : Walker's ... 83
Block Indicators : Winter's ... 89
Blocking Back 58
" Block," Positive and Negative
Working 29
Block Sections : Variable
Lengths 27
Block Systems : Three-Wire
and One-Wire 82
Breakdown Van Trains and
Engine Replacing or Assist-
ing Disabled Engine 60
Brighton Railway Company's
Signalling .. 6. 24
Bristol and Gloucester Railway
Company's Signalling 6
C.
" Call Attention " Signal,
34-35. 4#, 5°
"Calling On" Signals 115, 284
INDEX.
Cancellation of Signals 81
Cancelling Signal 62
Choice of Instalments 94
Circuit Arrangements for Special
Case 150
Circuit Arrangements for Typical
Block Sections 149
Clark's Double-Needle Signal-
ling Apparatus 8
Clark's Recommendations for
Signalling Apparatus 11
Classification of Block Indica-
tions 76-79
Classification of Railway Sig-
nalling 28
Clayton Tunnel Signalling 6, 24
Code Employed on Midland
Railway, Desford and Bags-
worth 7
Code of Signals and Alphabet
for Bains's Instrument 137
Comparison of Codes 70-73
Conditions Contributing to Acci-
dents 327
Cooke, Sir W. F., Estimate of
Value of Railway Signalling 26
Cooke and Wheatstone's Signal-
ling by Independent Instru-
ments ... 5
Gxjke and Wheatstone's Signal-
ling, Paddington, West Dray-
ton, and Hanwell 4
Cooke-Wheatstone's Signalling
System, Distinctive Feature 21
Cost and Maintenance, Relative 93
Course to be pursued when
Train is an Unusually Long
Time in Section 57
D.
Dial Signal Codes 35» 49
" Distant " Signal Lights,
Flashing of 304
" Distant " Signals 113
Disturbances of Instruments ... 91
Divisions of Electrical Signals .. 45
E.
Earlier Applications of Elec-
tricity to Train Signalling ... 3
Early Objection to Block
Systems I
Emergency Signals 45
Engines or Trains Coupled 55
Essential Qualifications of Block
Instruments 140
Examples of Rules Relating to
Hand, Fixed, and Detonating
Signals 124-136
F.
Failure of Instruments or Bell... 67
Fixed Signals 110-117
Fletcher's Three - Wire Com-
bined Block Apparatus 1 68
Fog Signalling 117-122,332
Fog Signalling by Electric Bells 334
Fog Signalling, Pigg's Method.. 335
Fog Signalling, Raven and
Baister's Method 337
Forms of Indicator 81
Four Hundred Yards Regula-
tion 51, 149
Gate Crossing Equipment for
Single-Needle Circuits 294
Great Northern Railway Com-
pany's Early Signalling 7, 24
Ground Discs 117
Growth of Applications of Elec-
tricity to Signalling 19
H.
Hand Signals no
Harper's One- Wire Block Appa-
ratus 166
Harper's Block Apparatus :
Character of Indications 168
INDEX.
Harper's Block Apparatus :
Paths of Currents 167
Head Lights 103
Home Signals 114
Independent Instruments for
Signalling, Cooke and Wheat-
stone's 5
Indications During Failures 90
Instruments Indicating Three
Conditions of Line 84
Instruments Indicating Two
Conditions of Line 84
Instruments Requiring Continu-
ous Currents for Maintenance
of Indications 82
Instruments Requiring Transient
Currents for Changes of Indi-
cations 82
Interlocking, King's Cross and
Belle Isle 323
Interlocking of Points and
Signals 122
" Is Line Clear :> Signals 48
J.
Junction Working 52
Lampman or Fog-signalman
required 69
" Line Blocked " 78
"Line Clear" 51.76
Liverpool Overhead Railway :
Actuation of Contacts by
Trains 365
Liverpool Overhead Railway :
Actuation of Signals 363
Liverpool Overhead Railway :
Arrangements of Terminal
Stations 376, 377
Liverpool Overhead Railway :
Comparative Degree of Safety
Attained 372
Liverpool Overhead Railway :
Cross-Over Road Working ... 370
Liverpool Overhead Railway :
Description of Operations for
Ordinary Working 367
Liverpool Overhead Railway :
Estimate of Cost of Electrical
Power for Signalling 380
Liverpool Overhead Railway :
Estimates of Electrical Power
Used for Signalling 379
Liverpool Overhead Railway :
" Making " and " Breaking "
Contacts 365
Liverpool Overhead Railway :
Position of Signals During
Failures 370
Liverpool Overhead Railway
Signalling 361
Liverpool Overhead Railway :
Signal Arrangements 361
L. and N. W. Co.'s Early
Signalling 22
M.
Manchester, Buxton, and Mid-
lands Junction Railway Sig-
nalling 6
Messages on Birmingham and
Gloucester Railway 6
Midland Company's Desford
and Bagsworth Code ... 7
Midland Company's Early Sig-
nalling 6
Minories and Blackwali Cable
Railway 4
Mixed Trains 69
Mode of Signalling by Block
Telegraph ... .. 50
Modes of Working with Diffe-
rent Classes of Instruments... 87
N.
Necessity for Automatic Notice
of Entrance of Train in Section 330
INDEX.
Necessity for all Classes of Sig-
nalling 342
Necessity for Regulation of
Traffic 2
N on- Uniformity of Space Limit 27
O.
1 Objects of Apparatus 27, 46
Objects of Whole System of Sig-
nalling 331
Obstruction Danger Signal 57
Opening and Closing of Cabin. . . 67
Opening and Closing of Signal
Cabins where there are Tele-
graphic Switches 67
P.
Parallel Lines 69
Permanent Electrical Indications 33
Permissive Block Working, 140, 278
Permissive Block Working :
Adaptation of Ordinary Single
Needle 281
Permissive Block Working :
Difference between Indication
and Condition of Line when
Clearing Line with Record-
ing Instruments 293
Permissive Block Working :
Difference between Tyer's and
Hampson's Instrument 290
Permissive Block Working :
Differences in Modes of Work-
ing Instruments Described ... 291
Permissive Block Working :
Hampson's Recording Instru-
ment 289
Permissive Block Working :
Indications of Instruments at
Sending End of Section 292
Permissive Block Working :
Single-Needle Instrument —
Indications Provided ... 282-283
Permissive Block Working :
Tyer's Recording Instruments 287
Permissive Block Working :
Single-Needle Instrument —
No Record of Number of
Trains in Section 284
Permissive Block Working :
Typical Instances... 279, 285, 288
Physical Qualifications of Drivers 3 1
Platelayers' Lorries going
through Tunnels 56
Points' Indicators ... 307
Preece's Institution of Civil
Engineers' Paper, 1863 9
Preece's One- Wire Block Appa-
ratus 161
Preece's Block Apparatus :
Concurrent Action of Signal-
men necessary for " Line
Clear" Indication 165
Preece's Block Apparatus :
Number of Indicators 1 63
Preece's Block Apparatus :
Paths of Currents 163-165
Preece's Three- Wire Block, 1862 9
Pigg's Locking for Single-
Needle Instruments 171-175
Position of Releasing Treadle
for Locked Instruments 175
Public Level Crossings 69
R.
Rail Contacts 309
Rail Contacts : Actuation by
First Vehicle 315
Rail Contacts : Buck's Patent... 312
Rail Contacts : For Prolonged
Contact 311
Rail Contacts : Hollins's Form. 317
Rail Contacts : Pigg's Form ... 310
Rail Contacts : Siemens's Form 313
Rail Contacts : Simple Form .. 310
Rail Contacts : Sykes's Form... 207
Railway Signalling, Classifica-
tion 28
Recording Time when Signals
Forwarded and Received 68
Regulations for Use of Sig-
nalling Codes 35-43* 5°-7o
INDEX.
Relations between Different
Classes of Signalling 342
Relative Importance of Indica-
tions 79
Relative Responsibility .. .. 327-332
Relative Responsibility : Driver
of Train 31
Relative Responsibility: Signal-
man at Receiving End 30
Relative Responsibility : Signal-
man at Sending End 29
Repeating Signals : Extended
Use 340
Repetition of Signals 50
S.
Saxby and Farmer's Interlock-
ing of Starting or Advance
Signal 191
Saxby and Farmer's ' ' Lock and
Block" ... 184
Saxby and Farmer's " Lock and
Block": Cancellation 198
Saxby and Farmer's " Lock and
Block": Description 185-196
Saxby and Farmer's " Lock and
Block " : Importance of Start-
ing Signal 197
Saxby and Farmer's " Lock and
Block ": Indications Provided 199
Saxby and Farmer's " Lock and
Block" : Interlocking with
Fouling Points 190
Saxby and Farmer's " Lock and
Block": Objects Aimed at... 185
Saxby and Farmer's " Lock and
Block " : Ultimate Control of
Starting Signal ..... 195
Siemens's Automatic Block Sig-
nalling System 344
Siemens's Automatic System :
Application to Junction Work-
ing 351
Siemens's Automatic System :
Description of Signalling
Apparatus ... 344
Section Clear but Station or
Junction Blocked 54
Section Obstructed by Accidents
or by Disabled Train S9'
Section of Line between Cabin
and Advance Signal, Indi-
cating Condition of 307
Shunt Train for Following Train
to pass 65,
Siding Signals 117
Signal Lights 112.
Signal Light Indicators 3°2
Signal Light Indicators : Indi-
cator and Alarm 3°3
Signal Repeaters 295.
Signal Repeaters : Contact Boxes 296
Signal Repeaters : Correct Posi-
tions for Contact Boxes 301
Signal Repeaters : Disc Form 296'
Signal Repeaters : Importance
of Indications During Failure
of Apparatus 298
Signal Repeaters ; Indications
Provided 295
Signal Repeaters : Needle Form 295,
Signal Repeaters : Number of
Wires Required 296
Signal Repeaters : Positions of
Contact Boxes 297, 299, 300
Signal Repeaters : Semaphore
Form 296'
Signal Whistles 101
Signals and Indications, Dis-
tinction ... 80
Signals for Distinguishing Trains 46 •
Signals, Permanent and Tran-
sient 33,
Signals, Special 46
Single Lines : Difference in
Character 254-255,
Single- Line Working 238
Single-Line Working : Addi-
tional Precautions Necessary 238
Single- Line Working : Arrange-
ments for Obviating Delay ... 245,
Single-Line Working : Com-
bination of Staff and Ticket
with Block Working 243,
Single- Line Working : Con-
sideration of Design of
Instruments for 277"
INDEX.
Single- Line Working : Conver-
sion of Line to "Up" or
" Down " at Will 276
Single- Line Working : Require-
ments of Instruments for
Single- Line Working 244
Single- Line Working : Staff
Sections 239
Single- Line Working : Staff and
Ticket Working 241
Single- Line Working : Staff
Working 240
Single- lane Working : Staffs
and Tickets 239
Single- Line Working : Tyers
Tablet Instruments 263
Single- Line Working : Tyers
Tablet Instruments, Descrip-
tion 263-275
Single- Line Working : Typical
Staff Sections 242
Single- Line Working : Unbal-
ancing of Staffs 255
Single-Line Working : Varia-
tion of Systems Required . . 278
Single- Line Working : Want of
Flexibility in Staff Working . . 244
Single-Line Working : Webb
and Thompson's Instalment,
Description 246-254
Single- Line Working : Webb
and Thompson's Instruments,
Advantages over Simple Staff 253
Single- Line Working : Webb
and Thompson's Instruments,
Paths of Currents 251
Single- Line Working : Webb
and Thompson?s Instruments,
Reliability 253
Single Line Working : Webb
and Thompson's Instruments,
Switching 256-263
Single- Line Working : Webb
and Thompson's Instruments —
When Concurrent, Action is
not Necessary 254
Single- Line Working : Webb
and Thompson's Train Staff
Instruments 246
Single-Needle Block Circuits ;
Diagram of Connections 154^
South - Eastern Railway Com-
pany's Early Signalling 7, 23.
Space Limit. ...» 27, 46-
Space Limit not Uniform or
Constant 27
Starting Signals 116
Stop and Examine Train 60-
Subsidiary Block Indicator,
Single-Needle 151
Swingbridge : Application of
Sykes's Locking to Single-
Needle Instruments 220-226
Swingbridge : Circuit Arrange-
ments 220
Swingbridge : Sectional
Arrangements 219
Swingbridge with Lines Bunched 218
Switching Single-Needle Block
Apparatus 152-158
Sykes's Block Apparatus : Bat-
tery Arrangements „. 214
Sykes's Block Apparatus : Can-
cellation 217
Sykes's Block Apparatus : Indi-
cator, Description 200-211
Sykes's Block Apparatus : Inter-
locking with Levers 206
Sykes's Block Apparatus : Junc-
tion Working .. 214
Sykes's Block Apparatus: Ob-
jects Aimed at 199
Sykes's Block Apparatus : Rail
Treadle 207
Sykes's Block Apparatus :
Results of Line Contacts 216
Sykes's Block Apparatus : Signal
Replacer 208-212
Sykes's and O'Donnell's Single-
Needle Block Apparatus 229-
Sykes's and O'Donnell's S N
Apparatus : Description.. 229-235-
Sykes's and O'Donnell's S N
Apparatus : Paths of Currents,
232-233^
Sykes's and O'Donnell's S N
Apparatus : Objects Attained,
235-238,
INDEX.
: Sykes's Electric Fouling Bar ... 318
Sykes's Signal Selector 320
Sykes's Three - Wire Block
Apparatus 199
T.
Tail Indicators ... 106
Telegraphing of Trains :
Minories and Blackwall Cable
Railway 4
Telegraphing of Trains : Pad-
dington, West Dray ton, and
Hanwell 4
Telephones on Block Bell Cir-
cuits 326
Testing Block Bells and Indica-
tors'Signal 68
Testing Controlled or Slotted
Signals 69
Thackley, Clay Cross, and
Duffield Tunnels Signalling... 6
Theoretical Conditions of Line 74
Time Signal 69
Timmis's Automatic Signalling
System 361
Timmis's Electrical Signalling
Apparatus, Earl's Court 380
Timmis's Electric Signalling,
Earl's Court : Actuation of
Points, Locking Bars and
Bolts, Semaphore Signals and
Ground Discs 380-387
Train Divided Signal 64
Train Messages 97
Train Messages, Use of Tele-
phone for 100
" Train on Line " Signal 44, 78
Train out of Section Signal 56
Train Passed without Tail Lamp
Signal 62
Transient Electrical Signals ... 33
Travelling Cranes 70
Tyer's Apparatus, 1852 7
Tyer's Block Apparatus : Char-
acter and Number of Indica-
tions 171
Tyer's One- Wire Block Appa-
ratus 170
Tyer's Tablet Instruments
Typical Block Sections 1 47 -
U.
Uniform System of Block Sig-
nalling, Desirability of 341
Use of Automatic Apparatus . . . 238
V.
Vehicles Running Away on
Right Line 66
Vehicles Running Away on
Wrong Line 65
Visual Outdoor Signals 109
W.
Walker's Block Apparatus :
Number of Indications Pro-
vided 161
Walker's Block Apparatus :
Paths of Currents 158
Walker's Block Apparatus :
Precautions Required in Use of 160
Walker's One - Wire Block
Apparatus 158
Walker's "Train Signalling in
Theory and Practice " 1 1
Webb and Thompson's Train
Staff Instruments 246
When Block Telegraphing may
be Suspended for Single-Line
Working 60
Wickwar Tunnel Signalling ... 6
Winter's One-Wire Block Appa-
ratus 176
Winter's Block Apparatus :
Description 178
Winter's Block Apparatus :
Paths of Currents 179-181
Winter's Apparatus : Objects
Aimed at 184
Winter and Craik's Electrical
Interlocking 183
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