Carrier Systems on Long Distance Telephone Lines

A previous Institute paper in 1921 gave a very complete r??sum?? of the activities of the Bell System at that time in the development of multiplex telephone and telegraph systems using carrier-current methods. A new type of carrier telegraph system was subsequently described in an Institute paper. In the present paper the authors describe developments which have resulted in improvements ments in the carrier telephone art since that time. 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.