GB344362A - Improvements in or relating to telephone systems - Google Patents

Abstract

344,362. Automatic exchange systems. ASSOCIATED TELEPHONE & TELEGRAPH CO., 1033, West Van Buren Street, Chicago, U.S.A. Dec. 3, 1929, No. 37058. Convention date, Dec. 10, 1928. Addition to 274,033, [Class 40 (iv), Telephones, &c.] [Class 40 (iv).] In a call-finder system of the kind described in the parent Specification, the constantly rotating testing switch has a number of sets] of wipers and delivers two trains of impulses to the finders, which are of the up-and-around type. Circuit operations. When one of the wiper sets encounters a calling line, the corresponding line relay 2, 4, 7, 9 or 11, pulls up and locks itself through 18 which grounds wiper 33 to cause impulses to be delivered to the vertical magnet 16 and relay 23 (which ensures a complete step at each impulse), energizes cut-off relays 1, 3, 6, 8 and 10, 5 which disconnects all the wipers P, and 21 which energizes 13. The impulse train is stopped when 33 encounters terminal 120 or 121 and so energizes change-over relay 22 which locks up, energizes 20, and grounds one of the wipers B corresponding to the line relay energized. As will be seen from the Figure, 1 or 2 rotary impulses are sent by B1, 3 or 4 by B2 and so on, 23 ensuring a complete step for each impulse as before after which circuits are made in parallel for allotting switch magnet 24, and relays 19, 14. 19 releases 7, 18 but holds the cut-off relays, and 14 switches through and busies the line. After a short interval 21 falls unlocking 22, 20 and 19 and releasing 24 which allows the allotting-switch wipers to move on. If the next finder is busy, 24 re-operates over P and opens its own circuit and so on. 19 reoperates in parallel with the magnet, holds 1, 3, 5, 6, 8 and 10 and disconnects 18 to prevent association of the common equipment with a calling line until a finder is allotted. If a connector seizes the line while the finder is being stepped to it, 14 is short-circuited and cannot switch through and on the relapse of 13 when 21 falls, release magnet 12 is operated. In the case of simultaneous calls by lines having the same rotary positions in the testing switch, only the line relay nearest to 18 is able to lock up. While the testing switch is passing a busy line its line wipers are cut off by one of the relays 1, 3, 6, 8, 10.