Carrier-Current Communication on Submarine 



Cables 



Los Angeles-Catalina Island Telephone Circuits ^ 



By H. W. HITCHCOCK 



Synopsis: Seven telephone channels and one telegraph channel on one 

 single-conductor deep-sea cable have been made possible by the employment 

 of carrier current on one of the two submarine cables across Catalina chan- 

 nel. This is the only application of carrier telephony to deep-sea cables 

 and the system is one of the shortest carrier systems (26 mi.) in commercial 

 operation; it provides more separate carrier channels (six) than has been 

 previously attempted; and it differs in other important respects from other 

 systems. This paper describes this carrier-current system. 



TN the commercial application of new developments in the electrical 

 -^ communication art, there are a few places which repeatedly call 

 attention to themselves. Notable among these is Catalina Island, 

 for it is probable that in providing telephone service across the short 

 expanse of water which separates Catalina from the mainland, more 

 novel improvements have been employed than at almost any other 

 point. 



The first commercial telephone communication with Catalina 

 Island was established in 1920 when a radio system was placed in 

 operation between Avalon and the mainland, the circuit being ex- 

 tended by wire to Los Angeles. This circuit was in use for several 

 years and featured in a number of transcontinental demonstrations, 

 including the one which was held at the opening of the service to 

 Havana over the Key West-Havana cables. 



The system is of considerable interest as it represents the only 

 instance in which radio has been used, in this country at least, to 

 form a portion of a toll telephone system for the general use of the 

 public. That it was reasonably successful is demonstrated by the 

 fact that on some days as many as 183 commercial telephone mes- 

 sages and a large number of telegrams were handled over it. The 

 system also proved to be one of the first popular broadcasting stations 

 and many letters were received from radio fans, often several hundred 

 miles away, telling of some of the amusing conversations which were 

 overheard. 



In 1923 the radio was replaced by two single-conductor submarine 

 cables. By that time the demands for service were too great to be 

 met by a single circuit, while the growing interest in radio broad- 

 casting, as well as the increasing interference from ship transmitters, 



1 Presented at the Pacific Coast Convention of the A. I. E. E., Salt Lake City 

 Utah, Sept. 6-9, 1926. 



636 



