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 207
A PRIVATE AUTOMATIC EXCHANGE 189 If the night telephone initiates a call, the lineswitch grounds theprivate normal wire PN which operates relay K. The latter cuts offrelay A to insure the circuit against being cut off. If during the time that the night telephone is calling, the operator inthe…
Telephone
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