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 312
itch in that office to extend the subscribers connection over an idletrunk circuit, similar to that shown in the above diagram, to the rural-lineboard. As soon as the second selector switch has completed the connec-tion, current flows from earth through one winding of the double-woundrelay of the… … Fig. 244.- -Circuit of trunk incoming to a rural-line switchboard from an automaticswitchboard. tor. It also closes circuit from earth through the line lamp, signallingthe operator, and circuit from earth through the 1000-ohm slow-actingrelay A to negative battery. Relay A closes circuit from earth…
Telephone
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