SHIP SETS FOR HARBOR SHIP-TO-SHORE SERVICE 715 



without disturbing connections. Adequate ventilation is provided as 

 well as protection against direct splashing from above. 



The power supply includes 12 volts for the filaments of the trans- 

 mitter, receiver and selective signaling unit; 200 volts for the plate 

 supply of the radio receiver, and 1,050 volts for plates of the tubes in 

 the radio transmitter. For efficient operation these voltages must be 

 held to reasonably close limits and experience has shown that wide 



Fig. 1 — Cabinet housing radio equipment; front panel removed showing left top 

 radio transmitter, right top radio receiver, ringing unit beneath. 



variations in the boat's power supply are to be expected. Therefore, 

 two forms of power supply are generally recommended : 



1. Motor generators for both transmitter and receiver; 



2. A 12-volt storage battery and charging unit with dynamotors for 



the plate supply of the transmitter and receiver. 



In the case of motor generators, two machines are provided, each 

 consisting of a driving motor and a double winding generator mounted 

 on a common cast iron base. The machines are of splash proof con- 



