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 174
itchboard. Functions of the Keys.—The circuit of this board is shown in Fig. 156.The throwing up of any two key handles in the upper horizontal row ofkeys switches the keys together and constitutes switching circuit No. 1.Throwing down the handles of any two keys in this row switches thekeys… … Fig. 155.—Cordless private branch switchboard. together and makes switching circuit No. 5. Throwing down any handlein the lower horizontal row of local line keys enables the operator to ringthat particular line. Throwing down either key handle in the lowerhorizontal row of trunk keys holds that…
Telephone
Internet Archive · California Digital Library · Public Domain Mark 1.0. Free to use for anything.
