Electron Tubes for the Transatlantic 

 Cable System 



By J. O. McNALLY,* G. H. METSON,t E. A. VEAZIE* and 



M. F. HOLMESt 



(Manuscript received October 10, 1956) 



Electron tubes 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 of the cable between Nova Scotia and Newfoundland contains re- 

 peaters developed by the British Post Office Research Station at Dollis Hill. 

 These repeaters are built around the type 6P12 tube developed at that re- 

 search station. The repeaters contained tn the section of the cable system be- 

 tween Newfoundland and Scotland are of Bell System design and depend on 

 the 175 HQ tube developed at Bell Telephone Laboratories. 



In this paper the philosophy of repeater and tube desigji is discussed, and 

 the fundamental reasons for arriving at quite diferent tube designs are 

 pointed out. Some of the tube development problems and the features intro- 

 duced to eliminate potential difficulties are described. Electrical characteris- 

 tics for the two types are presented and life test data are given. Fabrication 

 and selection problems are outlined and reliability prospects are discussed. 



INTRODUCTION 



Electron tubes suitable for use in long submarine telephone cables 

 must meet performance requirements that are quite different from those 

 imposed by other communication systems. In the home entertainment 

 field, for example, an average tube life of a few thousand hours is gen- 

 erally satisfactory. In the field of conventional land-based telephone 

 equipment, where the replacement of a tube may require that a mainte- 

 nance man travel several miles, an average life of a few years is considered 

 reasonable. In deep-water telephone cables such as the new transatlantic 

 system, the lifting of a cable to replace a defective repeater may cost 

 several hundred thousand dollars and disrupt service for an extended 



* Bell Telephone Laboratories, t British Post Office. 



163 



