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 438
Line SwitchDISTRICT STA. … MAIN OFFICE o CallingTelephone Fig. 312.—Showing switches and inter-office trunks used for a reverting sub-office. this apparatus is used the trunk from the sub-office to the main office isoccupied until by the selection of the desired 1000 or 100 group thecalling subscriber indicates that the…
Telephone
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