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 64
rs line at the connector bank so that noconnector can seize this line. The operation of the lineswitch circuit (Fig. 46) proceeds as follows:When a subscriber lifts his receiver from the switch hook the circuit isclosed from earth at the lineswitch through spring (a) to the positiveside of line to… … Fig. 45.—Master switch mounted on shelf of Keith lineswitch unit. As soon as this circuit is established the line relay attracts its armature,closing the circuit from ground through the pull-down coil, P.D.C.,to open-main battery bus bar, which is always connected to the nega-tive pole of battery…
Telephone
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