222 MODERN PAPER-MAKING between the first and second shafts is at once shown by movement of the regulator. Correction of an error in section motor speed is made very quickly, the response of individual regulators being designed to take into account the differing characteristics of inertia and fiictional damping to give maximum drive sensitivity without hunting, the accuracy of control being such as to avoid strain on the web of the paper. A view of the differential regulator unit and the small synckonous motor [Siemens Schuckert FIG. 91.—VARIABLE SPEED ELECTRIC REEL-UP, ENABUNG HARD OR SOFT ROLLS TO BE MADE is shown in Fig, 89. The differential gears are housed inside the regulator case, while the cone pulley shaft projects at the back of the case. In Fig. 90 is shown a typical section motor with interlock equipment and cone pulley transmission to enable the draw of the section to be varied. Suppose the belt is in position as shoton in the illustration and it is required to alter the draw by decreasing the speed of the motor, the belt must be moved by means of die bdt-dbifter towards the large diameter of cone on the motor shaft; this increases the speed of the second shaft of the differential gear and causes the regulator to move and reduce the speed of the motor until the second shaft co- incides ia speed with the first shaft. The regulator arm has now assumed a new posttkm CHI tfac fece-plate, giving the required field strength for the new speed. Tfje