SWITCHING EQUIPMENT 



585 



keeps on ringing and the signal remains illuminated until the 

 machine operator acknowledges the signal by pressing the cor- 

 responding button on his equipment. The connection diagram 

 for a small equipment of this type is shown in Fig. 377. 



It is, of course, not necessary to install the signals near the 

 machines on pedestals. They are often located on the nearby 

 wall where they can easily be seen, and occasionally various 

 colored lamps are installed at the side of the respective signals so 

 that they can be read more quickly and distinctly from a distance. 

 One company, for example, uses a blue light beside the " stand- 



- + 125 Volt* 





Relay and 

 Gong 





c 



j \- -h"i r" "T " ~t~"~~i 



Q 6 Q ! ! OO O^ 1 * 



! 4olJiiMJ sa - 



m* 



Machine Stand 



Machine Stand 



| j I y 



FIG. 377. Connection Diagram of Two Signal Equipments with Three Signals 



by " signal, a red for the " fast," a green for the " slow " and 

 white for all the others. 



What the signals should read depends, of course, to some 

 extent on the local operating conditions. The following are, 

 however, very common: "Stand-by," "start," "fast," "slow," 

 " stop," and " O.K." These are used in the power-house of the 

 Pennsylvania Water and Power Company, their meaning being as 

 follows : 



" Stand-by ": Stand near governor and await further orders. 

 Correct any apparent governor trouble. Trouble impending. 



