Electron tubes for the transatlantic cable system

Thermionic valves for use in repeatered underwater telephone cable systems must be capable of operating for many years with a reasonable probability of proper functioning. In the new transatlantic telephone cable system, the section between Nova Scotia and Newfoundland contains repeaters developed by the British Post Office Research Station and built around the type 6P12 valve developed there. The repeaters contained in the section between Newfoundland and Scotland are of Bell System design and depend on the 175HQ valve developed at Bell Telephone Laboratories. In the paper the philosophy of repeater and thermionic valve design is discussed, and the fundamental reasons for arriving at quite different valve designs are pointed out. Some of the valve development problems and the features introduced to eliminate potential difficulties are described. Electrical characteristics for the two types are presented and life-test data are given. Fabrication and selection problems are outlined and reliability prospects are discussed.