A versatile power-line-carrier system

F. M. Rives (General Electric Company, Schenectady, N. Y.): The general idea of providing several simultaneous telegraph or signal channels by modulating a single carrier with several closely spaced audio tone frequencies has been used for many years in wire-line telegraph practice. Its first use in power-line carrier practice dates back only a few years; one of the first installations involving modern equipment of this type was described in a paper presented at the 1942 AIEE winter technical meeting.1 However, the numerous advantages of multiple-channel audio-tone systems, particularly in providing additional joint-use or simultaneous functions, have not received adequate treatment previously, and the authors of this paper are to be commended for their contribution to this subject.