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 106
Fig. 79.—Circuit of outgoing secondary lineswitch, Keith type. the choke relay pulls up and short-circuits all of its wnding except 18ohms, becoming little more than a conductor. Outgoing Trunk Secondary Lineswitches.—Both types of line-switches, Keith and rotary, have been used on outgoing trunks…
Telephone
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