No abstract

Synopsis: Two previous papers before the American Institute of Electrical Engineers discussed the activities of the Bell System in the development of multiplex telephone and telegraph systems using carrier current methods. The present paper describes developments which have resulted in improvements in the carrier telephone art during the past few years. A new, so‐called type “C” system is described in detail, together with suitable repeaters and pilot channel apparatus for insuring the stability of operation; the line problems are considered and typical installations pictured. The growth of the application of carrier telephone systems and their increasingly important part in providing long distance telephone service on open‐wire lines are shown.