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 294
the operator presses key K-7. Thispulls up relays 72-49 and 72-50. Relay 72-50 on energizing connects theoperating wires 346-347 to the vertical and rotary relays and connectsthe winding of relay R-50 to the private wiper to be used as a trunk-finding circuit. Relay 72-49 opens the protective loop… … Aufo. ManualSelectors Fig. 233.—Trunk to manual office. position. The current flow in this circuit is as follows: negative battery,front contact of relay 72-49, wire 345 to Fig. 225, wiper TF-83, back contactof relay 72-31, back contact of relay 72-35, winding of relay 72-36, wire 140,to the…
Telephone
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