Carrier systems on long distance telephone lines

The authors describe recent activities of the Bell System in the development of long distance multiplex telephone systems using carrier current methods. A new, so-called type C system which supplants earlier types of equipment 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.