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BELL SYSTEM TECHNICAL JOURNAL 



secured by electrically operated latches unless the wheel is in the 

 grounded position. Door switches are provided in the control circuits 

 which prevent the transmitter from being placed in operation unless 

 all doors and windows are closed. 



The power panel and rectifier assembly is shown in Fig. 5. The 

 general arrangement corresponds to that of the transmitter proper 

 and similar safety features are provided. In the power panel, which 

 is on the left, are centralized the necessary power distribution and 

 control facilities. The equipment requires a 3-phase input of approxi- 



Fig. 5 — -Power panel and rectifier assembly for SO-kw radio transmitter. 



mately 250 kw. at 440 volts. The control arrangement is such that 

 the transmitter can be started and stopped by means of a single set 

 of push buttons, the various circuits being energized in proper sequence 

 by means of suitable relays and contactors. The central unit is a 

 three-phase half- wave rectifier supplying power at 1,600 volts to the 

 plates of the air-cooled tubes. The six-tube rectifier on the right 

 supplies plate power at 17,000 volts for the water-cooled tubes. The 

 filament and plate transformers and smoothing filter for the latter 

 are located in the power room on the floor below. The filter consists 

 of two units, one for each side of the push-pull circuit, employing a 

 6-/if condenser and a 12-henry inductance. Two 24-volt, 550-ampere 

 direct generators (one a spare) supply power to the filament circuits. 



