Hawkins electrical guide ... : questions, answers & illustrations : a progressive course of study for engineers, electricians, students and those desiring to acquire a working knowledge of electricity and its applications ; a practical treatise (1914)
Hawkins, N. (Nehemiah), 1833-1928 · New York : T. Audel & Co. · leaf 51
Pig. 2,951.—Wiring diagram showing two telephones with a listening key at the main instru-ment to cut off the extension station. This key can be placed at either instrument andthe extension wired to either inner or outer contacts. As shown the key is at the mainstation and the extension is on the… … Pig. 2,952.—Wiring diagram showing private line extension station circuit from P.B.X.switchboard, whereby absolute secrecy with outside exchanges is obtained. When exten-sion listening key is normal, extension signals operator in same way as do all other exten-sions. After asking for private…
Electrical engineering
Internet Archive · Brigham Young University · Public Domain Mark 1.0. Free to use for anything.
