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
circuit through the bridge relay is broken by the release of theconnector switch at central office the circuit is broken through the 1300-ohm release-control relay. When the armature of this relay falls backcircuit is broken through the polarized supervisory relay and as a resultthe local… … NIGHT KEY Illl^! Fig. 169.—Circuit through an automatic P.B.X. attendants cabinet (non-secret).
Telephone
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