TRANSOCEANIC TELEPHONE SERVICE 273 



desk, (3) the radio transmitting set containing the oscillators, modu- 

 lators, and power amplifier, (4) a power control board, (5) rectifying 

 apparatus and filters for supplying direct current at 10,000 volts, (6) 

 motor-generators for providing various circuits with direct current, (7) 

 water circulating pumps, tanks, and cooling units. 



The wire terminal equipment and repeaters at the transmitting 

 station are standard units mounted on relay racks beside the voice 

 frequency testing apparatus common for all channels. 



The voice frequency control desk provides facilities by which the 

 attendant can monitor the incoming voice currents and the outgoing 

 radio signal. Means are provided for observing the volume of these 

 signals. Oscillators are provided for the purpose of quickly checking 

 the performance of the system during line-up periods and for sending 

 Morse signals over the radio link when required. The control desk 



Fig. 2- — Front view of short-wave radio transmitter of type used at Lawrenceville. 



is also equipped with apparatus for direct telegraph communication 

 with the technical operator at New York. 



The radio transmitter consists of seven independently shielded units 

 mounted on a common sub-base to form a single assembly, 4 ft. by 20 

 ft. by 7 ft. high. Some of the units are subdivided into several small 

 shielded compartments. Very effective electrical screening or shield- 

 ing between the various parts of a short-wave transmitter is essential. 

 Otherwise stray fields introduce unwanted feedback couplings which 

 produce distortion effects and spurious oscillations. Fig. 2 is a front 

 view of the transmitter. Beginning at the left there are two units for 

 speech amplification, one for radio frequency generation and modula- 

 tion, one unit each for the first stage, the interstage circuit and the 

 last stage of radio-amplification, and a double-sized unit for the output 

 circuit. It is interesting to note that the over-all length of this as- 



