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 286
e hundred may initiate a call. The unlocking and falling back of the contl relay 72-13 of the priminaryselector (Fig. 224) takes the negative battery potential from wire 45 sothat any other key-set switch will not stop on this trunk. The pullingup of the signal relay 72-34 (Fig. 225) at the… … Fig. 227.—Sending machine and keyset circuit. The operator now answers the call by pressing the listening key L-K(Fig. 227). Current then flows from ground (Fig. 181) contact of keyL-K and wire 125 to (Fig. 225) winding of listening relay 72-33, backcontact of relay 72-31, back contact of relay…
Telephone
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