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 377
S4IOAQf everything in the switch, excepting the release magnet, which draws itscurrent through a release signal relay which is common to all the con-nectors on this lineswitch board. Each master switch has its own pair of wires supplying positive and POWER PLANT, SUPERVISORY AND TESTING EQUIPMENT…
Telephone
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