The New York-London Telephone Circuit 



By S. B. WRIGHT and H. C. SILENT 



Synopsis: This paper discusses the special provisions which are in use 

 on the transatlantic telephone to compensate for the variability of the 

 wire and ether paths, for the radio noise, and for the fact that two-way 

 transmission is effected upon a single wave-length. So-called technical 

 operators are in attendance at each end of the radio path and are equipped 

 to adjust the magnitude of the speech currents entering the radio trans- 

 mitters to such a value as to load these transmitters to capacity. The 

 amplification introduced at the radio receivers can also be adjusted to 

 compensate for changes in the transmission efficiency of the radio paths. 

 Finally, voice-operated relays together with suitable delay circuits are 

 provided which so control the apparatus that at any given time it can 

 transmit in but one direction. By this arrangement, a speaker's voice 

 upon leaving his transmitting station cannot operate his own receiver 

 although this is tuned to the transmitting wave-length. 



TO the telephone subscribers who use the New York-London 

 circuit the procedure of making a call and carrying on a conver- 

 sation is as simple as that of any long distance telephone call. Even 

 to the telephone operator who establishes a transatlantic connection 

 there is little to differentiate the New York-London "wire-radio-wire" 

 circuit from the hundreds of other circuits which appear as mere jacks 

 on the switchboard in front of her. Beyond this point, however, there 

 is an organization of physical plant, personnel and procedure very 

 much different from the usual long distance telephone circuit. 



Without going into any description of the radio portion of the New 

 York-London circuit, which has been adequately treated in previous 

 articles, this paper describes some of the interesting features of the 

 circuit, including the method of electrical operation which has been 

 worked out for making possible two-way talking in the usual way, in 

 spite of difficulties introduced by "static," transmission variations and 

 difficulties brought about by the use of the same "frequency band" 

 for transmission in both directions. The method of operation involves 

 manual adjustments of controls at the radio stations and at the circuit 

 terminals, and automatic switching by means of vacuum tube-operated 

 relays controlled by the voice currents of the telephone subscribers. 

 The voice-operated relay system is particularly interesting, and is, 

 therefore, rather fully described. 



Before the operation of the circuit is described a brief general picture 

 of the system will be given. Fig. 1 shows its geographical layout, and 

 gives an idea of the relative lengths of wire and radio circuit involved, 



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