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 296
Fig. 236.—Rotary switch. … Fig. 237.—Relay. windings directly to the line, independent of relay R-45. The movementof main spring r-441 causes the lighting of the lamp L-10. The B operator in the manual office, on receiving the number, 18 274 A U TOM A TIC TELEPHON Y makes the busy test in the usual way and if the line is…
Telephone
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