Electron Tubes for the Transatlantic Cable System

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 generally satisfactory. In the field of conventional land-based telephone equipment, where the replacement of a tube may require t h a t a maintenance 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, f British Post Office. 1G3 164 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1 9 5 7 period of time. These factors suggest as an objective for submerged repeaters t h a t the tubes should not be responsible for a system failure for m a n y years, possibly twenty, after the laying of the cable. Such very long life requirements make necessary special design features, care in the selection and processing of materials t h a t are used in t h e tubes, unusual procedures in fabrication, detailed testing and long aging of the tubes, and the application of unique methods in the final selection of individual tubes for use in the submerged repeaters. As indicated in the foreword and discussed at length in companion papers, the British Post Office developed t h e section of the cable system between Clarenville, Newfoundland, and Sidney Mines, N o v a Scotia.