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
sub-office, in which the call originated, when the connectorswitch trunk is occupied. Therefore, as indicated in Fig. 312, such aconnection occupies two trunks between the sub-office and its main office. Where conditions warrant the use of somewhat more complicatedand expensive sub-office… … Line SwitchDISTRICT STA.
Telephone
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