Transcontinental Telephone Lines

ESS than twenty-five years ago, it was impossible to talk by telephone from coast to coast across the United States. Furthermore, it was impossible to talk between points separated by any such distance anywhere in the world. By 1915, technological advancement had reached a point such that telephone service could be established across the country, and three telephone circuits had been built which connected San Francisco and the Pacific Coast with points in the East. Four telegraph circuits were also provided by the new wires. An improved loading system and especially the successful development of the vacuum-tube telephone repeater were outstanding factors which made telephone connections of such length possible for the first time in history. Open-wire lines played the major role in the early transcontinental telephone circuits. The transmission losses caused by cable were so great that it was avoided whereever possible. The steady improvement of telephone repeaters, types of loading for use on cable circuits, and carrier telephone systems for use on open-wire lines made it possible to provide rapidly and economically more telephone circuits across the continent as use of the service grew. In the cross section * This paper has been prepared from an address given before the Communications Group of the A. I. E. E., New York Section, March 22, 1938, and published in Electrical Engineering for October, 1938. Since the paper was written, three type J 12-channel carrier systems have been placed in service on the new line.