Experience in Applying Carrier Telephone Systems to Toll Cables

Experience in Applying Carrier Telephone Systems to Toll Cables By W. B. BEDELL, G. B. RANSOM and W. A. STEVENS T HE application of carrier telephone systems to toll cable conductors, particularly those conductors in existing cables, is expected to become an important means of providing additional long distance telephone circuits. Eight hundred and thirty-seven route miles have been equipped in the United States to date, and 17 twelvechannel systems have been placed in service, providing a total of about 58,000 circuit miles. Late in 1939, 200 additional route miles are expected to be completed which, together with additional systems on existing routes, will add nine systems and about 48,000 circuit miles to the above figures. The type of carrier system which has been installed is t h a t described by Messrs. C. W. Green and E. I. Green before the American Institute of Electrical Engineers in 1938, and which is now designated as type K. 1 The problems incident to the application of this system to toll cable conductors may be of general interest and it is the purpose of this paper to describe some of these. This description will start at the point where traffic needs have indicated that additional circuits should be provided along a given route and economic and other considerations have shown t h a t they should be provided by means of type K cable carrier telephone systems. For specific examples, reference will be made to the New York-Charlotte and Detroit-South Bend projects, in which sections the application of the initial type K carrier systems has been completed.