CARRIER-CURRENT COMMUNICATION 637 



rendered its continued operation very difficult and unsatisfactory. 

 The sul)marine cables were of the single-conductor, deep-sea type, 

 each providing a single-wire circuit. They are of interest for a num- 

 ber of reasons, chiefly, perhaps, because they represent one of the 

 few instances of deep-sea cable manufacture in this country. From 

 the cable hut at San Pedro, the circuit is extended to the office by 

 means of a special lead-covered cable containing four individually 

 shielded No. 13 B & S gauge pairs for the telephone circuits and four 

 19-gauge pairs for the telegraph circuits and other miscellaneous uses. 

 Between the San Pedro office and Los Angeles, the circuit was com- 

 posed of a No. 19 B & S gauge cable phantom. At San Pedro a through- 

 line repeater was inserted in order to secure the desired over-all equiva- 

 lent between Avalon and Los Angeles.'- 



Although the two circuits provided by the cables represented a 

 great improvement ov^er the previous condition as regards the quality 

 of the service rendered and the number of messages which could be 

 handled, it was realized that they would soon prove inadequate to 

 handle the heavy summer business, for which eight or ten circuits 

 would be required in a relatively short time. To provide for such a 

 large increase by the laying of additional cables was deemed imprac- 

 ticable, as the cost would be excessive. Furthermore, in water of this 

 depth — 3,000 feet — it is important that cables be laid at least a mile 

 or two apart, so that in the event that trouble develops on one, it 

 can be repaired without disturbing any of the others. For a total 

 distance as short as the width of the Catalina channel — 23 nautical 

 miles — such a separation between adjacent cables could not be main- 

 tained without materially increasing the length of the outer ones with 

 a corresponding increase in their cost and in their transmission equiva- 

 lents. In view of these facts, it w^as decided to secure as many more 

 circuits as possible by operating carrier systems over the two cables 

 already in use. This project was actively promoted with the result 

 that on May 15, 1926, six carrier telephone circuits were placed in 

 operation. 



The use of carrier in the past few years has increased so rapidly that 

 the mere addition of a new system is, in itself, of hardly more than 

 passing interest. In this instance, however, there are a number of 

 factors which render the project of particular interest. It is one of the 

 shortest carrier systems — 26 miles — in commercial operation. It is the 

 only application of carrier telephone to deep-sea cables; the system pro- 



- A description of these cables and their laying was given in a paper presented 

 by the writer at the Pacific Coast Convention in 1923 and published in Volume 

 XLII of the Transactions. 



