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 99
uses relay D-\ in the distantoffice to pull up, switching the trunk to a selector in section 1, leading tooffice No. 1. If the subscriber calls the second level on the selector in the originatingoffice, its wipers will rotate in on the second level and seize the first idletrunk. Relay A-2 in the… … I Chain RelaysFig. 75.—Quad-level repeater and trunk circuits. The other levels cause the direction of calls to sections 3 and 4 in asimilar manner. It is not necessary to use four groups—three or two can be arrangedjust as well. By using the ten-level 20-trunk selector, 20 trunks in one group…
Telephone
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