TRANSOCEANIC TELEPHONE SERVICE 



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tions separately and in each case to consider briefly the system and 

 apparatus of one channel before describing the general station plan. 



Transmitting System 



The four channels at Lawrenceville are equipped with independent 

 transmitters using certain auxiliary apparatus in common. Each 

 channel involves a radio transmitter with its associated power plant 

 and wire equipment, and a group of directive antennas designed and 

 adjusted for the specific wave-length assignments of the channel. 



The general method of transmission, with the exception of directional 

 sending, is the same as that employed for program broadcasting sta- 

 tions in that the radiated signal contains the carrier and both sidebands. 

 Systems in which one or more of these components are suppressed at 

 the transmitter appear to offer further means of improving short-wave 

 transmission, and the necessary apparatus for the practical application 

 of such systems when operating at frequencies in the order of 20,000 



DIRECTIONAL 

 ANTENMA 



PIEZO-ELECTRIC 

 OSCILLATOR 



HARMONIC 

 GENERATOR*! 



HARMONIC 

 GENERATOR *2 



Fig. 1 — Block schematic of transmitting system. 



kilocycles is undergoing development. However, throughout the 

 development of the transmitters as now installed at Lawrenceville the 

 possibility of future major modifications in the method of transmission 

 has been kept in mind. For this reason the modulator-amplifier 

 system was adopted. In this system the signal which is to be radiated, 

 is prepared by modulation processes at relatively low power levels and 

 thereafter amplified the requisite amount. The amplifier and its 

 power plant, representing a large proportion of the investment in 

 equipment, can be continued in service with no appreciable alterations, 

 even though the system of transmission and the modulating apparatus 

 undergo radical changes. 



The general scheme of transmission is shown in Fig. 1. After passing 

 through the line terminal and control apparatus, which includes 



