Patent GB-670252-A (GB)
Title: Switching system comprising multi-switches for establishing one or more connections in line finder and final selector stages
IPC: H04Q3/00
Filed: 1948-10-19
Abstract: 670,252. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. Oct. 19, 1948 [Oct. 20, 1947], No. 27118/48. Class 40 (iv). The multi-switch described in Specification 658,295 is used in one system for line-finding or as final selector in another system. Operation of final selectors, Figs. 2, 3, 5. The final selector is seized in the manner described in Specification 661,884, when a characteristic potential on wire e is sensed by the register-controller, a direct current test also being applied over wire d. The register-controller then closes contact A, which operates relay Ar, Fig. 2, which grounds common lead 1 to energize power magnet P1, Fig. 3, which rotates the common carriage of the switch to carry wipers I, II, III over contacts corresponding with the subscribers' lines. A tens setting is first made as described in Specification 563,666, a characteristic potential being detected on wiper III and transmitted over wires c, d to the register-controller so that when it matches the discriminating potential supplied by contacts yar, tube SV2 ionises in known manner to energize Wpr, Tsr, the latter stopping the carriage in the selected tens position and energizing relay Dr. Relay Wpr adjusts the register-controller to control the units setting by resetting the discriminating device with relay Yar (not shown) released. The carriage then hunts for the units setting in a similar manner, correspondence of potentials stopping the carriage to re-operate Wpr, Tsr, Dr. The opening of contacts wpl operates relay Br in series with Ar. The line is now double-tested and then treated for free or busy condition in known manner, a successful test energizing relay LFR, Fig. 5, to operate magnet H in the final selector which causes the through connection to be made in the manner described in Specification 661,884, contact R1 releasing Ar, Br to disconnect the common circuit of Fig. 3 from the final selector. Conductors a-d are now connected through to the subscriber's line circuit which is brought into talking condition by battery on conductor c. Connection to P.B.X. If a first P.B.X. line is selected and found busy, relay Phr operates in the register controller in known manner to start the selector hunting for a free line in the P.B.X. group. Relay Phr connects the anode circuit of a tube in a static switch, Fig. 5, to relay Ftr and conductor b, which is disconnected from the phase discriminating circuit so that Tsr, Dr, Fig. 3, release and magnet P1 reoperates to drive the wipers I-III over terminals of the P.B.X. group, the static switch testing the conditions successively applied to conductor d. As soon as a free line or the last line of the group is encountered, the static switch responds, relays Ftr, Tsr pulling up, the latter releasing P1 to stop the carriage. Plurality of calls to same P.B.X. group. Free P.B.X. lines have ground connected to conductor d. Busy condition on first P.B.X. line is indicated by 21 volts, and busy condition on second and subsequent lines by 37 volts, which is normal busy potential for individual lines, as described in Specification 663,037. When further P.B.X. lines exist, however, relays Dr, Er operate to cause a potentiometer to supply 21 volts to wiper II to cause further hunting. When the last P.B.X. line has been seized, any further call finds 7 volts on conductor d to cause the register to break down the connection to the selected line and supply busy tone to the calling subscriber. Line-finders, Figs. 1, 3, 4. Closure of contact A in the register-controller energizes relay Ar to operate power magnet P1 to drive the carriage, the potential detected by wiper I being applied over conductor c to the static switch which responds when a calling line is found to energize Ssr in the register-controller and Tfr in the common circuit, Fig. 3, over conductor b. Tfr halts the carriage and operates Fr, Dr to apply a double-test, a successful test operating relays Dtr, Dhr in the register-controller. Dhr operates Tdr to cause Br to pull up in series with Ar, whereupon a test is made over conductor d to determine whether the line has been seized meanwhile by a final selector. If the line is free, the static switch operates Lfr which reconnects ground to conductor a to operate magnet H which prepares the through-connection by energizing power magnet P2, contact R1 releasing Ar, Br to release the common circuit. If a line is simultaneously sought by a final selector and a line-finder, preference is given to the line-finder by operation of relay Gr. Specifications 577,088 and 641,819 also are referred to.