Automatic telephony; a comprehensive treatise on automatic and semi-automatic systems (1921)
Smith, Arthur Bessey, b. 1875, Campbell, Wilson Lee · New York : McGraw-Hill · leaf 199
NIGHT KEY Illl^! Fig. 169.—Circuit through an automatic P.B.X. attendants cabinet (non-secret). … NIGHT KEY Fig. 170.—Circuit through an automatic P.B.X. attendants cabinet (secret). connects the trunk directly to a line which may lead to any local station.At the same time, it disconnects the line of this particular telephone fromthe local switchboard. PRIVATE AUTOMATIC EXCHANGE 183 Another…
Telephone
Internet Archive · California Digital Library · Public Domain Mark 1.0. Free to use for anything.
