144 



ALTERNATING CURRENTS 



to move over the face of the dial-plate, as shown in Fig. 107, indicates 

 by the direction and speed of its rotation whether, and by how much, 



LAMP 



TWO-PHASE WINDING 



or STATOR(OR ROTOR) 



FIG. 106. Connections of Rotary Synchronizer. 



the incoming machine is running fast or slow. The proper time of 

 closing the main switch is when the pointer is vertical and stationaiy, 

 or moving with extreme slowness. 



FIG. 107. Dial-plate and Pointer of Rotary Synchronizer. 



A very useful feature of this instrument is the ingenious visual 

 engine-driver's signal. In the upper part of the dial-plate, Fig. 107, 



