Railroads

3914

Railroads

Central operates with electric locomotives and
multiple unit cars out of its Grand Central
terminal in New York, and the New York
New Haven, & Hartford similarly and as far
as New Haven, a distance of 70 m. The Penn-

Semaphore Signal at Proceed^

sylvania, a pioneer in this field, operates
man}' miles of its vast system by electricity,
using both electric locomotives and multiple
unit trains; while the Long Island, using
the same station for its business to Long
Island, uses multiple unit trains, operating
over 139 miles. The Chicago, Milwaukee,
St. Paul & Pacific is the leading example of
trunk-line electrification, operating 682 m. of
transcontinental line.

la order to run a number of trains safely
over a single piece of track, either in the
same direction or in opposite directions, some
method must be adopted for keeping the
trains either a fixed distance, apart or a fixed
time apart. The latter is at best a substitute
for the former, yet it has been the character-
istic system in use in the United States.
It is called the train-order system in distinc-
tion from the former, or block system.

Train-order System.—Ai some central
point on the road is located a train dis-
patcher, who is in telegraphic communica-
tion with all important stations along the
line. A schedule of all regular trains is made
out, giving the leaving time, time of passing
each station along the route, and, if it be a
angle-track road with trains running in both

directions, the fixed meeting points, which
are arranged to give a minimum delay to
all trains. Each employee concerned is pro-
vided with a copy of this schedule or oper-
ating time-table, and trains are operated in
accordance with it.

Automatic Block Signals.—These are in
more extensive use in the United States than
elsewhere and their use is increasing rapidly.

In the automatic signal installation, the
two rails are insulated from each other and
at the ends of the blocks are insulated from
the rails of the adjoining block. An electric
battery at the outgoing end supplies current
which flows through one rail to the entering
end, thence through a magnet of a relay con-
trolling the movement of the signal at that
point and back through the other rail to
the battery. With the current flowing thus
the signal is held in a clear or proceed posi-
tion. When a train enters the block, how-
ever, the current in the rails, tending to take
the path of least resistance, which is through
the wheels and axles of the train, is short
circuited from the relay. This short circuit-
ing de-energizes the signal relay magnet and
allows the relay magnet to drop, causing the
signal to fall to a horizontal or stop posi-

Color Light Signa^

tion behind the train. The signal arm is
counterbalanced to assure its' falling to a
natural horizontal position, or, in other
words, power is required to move or to hold
it in any other position. Thus, if axty ob-