Power Apparatus in the U.S. Telephone Industry

A survey of power systems and apparatus now used in U.S. telephone systems, both Bell and non-Bell. Operating features of large dc plants are reviewed and differences between Bell and non-Bell practices are noted. The characteristics of some typical rectifiers and power supplies are listed. Dc to dc converters in general use are compared with 20 kHz designs recently introduced. The history of ringing generators, single-frequency and multi-frequency is outlined, and the introduction of solid-state ringing plants noted. A recently introduced power plant which uses a 140 volt battery for reserve power is listed as a significant development.