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 318
RBAN EQUIPMENT 293 over the operating trunk, P-l. The talking circuit, indicated by theheavy lines, is entirely separate from the rest of the selector. When a connection has been extended to this switch, the operatingrelay OpRy is energized and in turn pulls up the release relay RlRy. Therelease… … Fig. 250.—Toll third selector (transmission selector). At each interruption of the calling device in the sleeve of the toll cord,the line relay drops back and operates the vertical magnet in series withthe series relay SeRy through a back contact on the switching relay SwRy,and a front contact on…
Telephone
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