SWITCHBOARDS AND SWITCHBOARD APPLIANCES. 323 



measure the voltage of any one of the three phases, as may be 

 seen by tracing the connections from the potential receptacle and 

 potential plug to the voltmeter in Fig. 275. The synchronizing 





receptacle is a plug switch into which the two forms of " syn- 

 chronizing plug " may be inserted, namely, the " starting plug " 

 and the " running plug." 



