GB289532A - Improvements in or relating to telephone systems - Google Patents

Abstract

289,532. Automatic Telephone Manufacturing Co., Ltd., Passmore, W. O., and Beale, C. E. Jan. 37, 1927. Automatic exchange systems.-A two-directional finder-switch adapted to hunt freely in both directions has operating potential supplied to its self-interrupting magnets over a wiper of a distributor. The finder-switch comprises two relays only, which are energized in two different circuits at different stages in the operation. Outgoing call. When the calling subscriber takes up his receiver, his line relay 4 operates, connects earth at 5 to busy the line in the connector banks, earths the contact 14 corresponding thereto in the bank of the wiper 21 of the linefinder, and connects earth at 8 through the distributor wiper 22 to the self-interrupting vertical magnet 30 and the lower winding of relay 32. Relay 32 opens the release magnet circuit at 35, and the rotary magnet circuit at 37; the line is also switched through at 33, 34, but this is ineffectual since the finder is not on the contacts of the calling line. The line-finder wipers are stepped up until the contact 14 is reached, when changeover relay 26 energizes over its upper winding. breaks the circuits of the vertical magnet and relay 32 at 29, locks itself to the starting earth at 8 and opens another point 31 in the release magnet circuit. When relay 32 releases, the wipers are stepped by the rotary magnet 38 until the wiper 20 reaches contact 17, when relays 10, 32 energize in series, cutting the rotary magnet circuit at 37, and the line relay circuit at 12, 13, and inserting a resistance 9 in the circuit of relay 10 to mark the line engaged to other finders. The calling line is switched through at 33, 34 and earth is fed back over conductor 41 from the first selector to hold relay 26 over its lower winding, and to energize the selfinterrupting magnet 25 of the distributor so that it steps on to select an idle line-finder. The magnet windings are of high resistance to allow of self-interruption. Release. When the subscribers hang up, earth is removed from conductor 41, de-energizing relay 26 and rendering the finder selectable to the distributor. Relay 26 cuts the circuit of relays 10, 32 at 27, and the release magnet 40 operates over off-normal contacts 39. Incoming call. The connector earths conductor 3 to energize relay 10 which cuts off line relay 4 to prevent a finder starting up when the subscriber answers. Failure to find. The tenth level of the finder is permanently earthed and the wipers are rotated therein to the eleventh contact to give an alarm or to initiate release. Two sets of wipers. To deal with a group of 200 lines, each finder would require an additional set of wipers and a wiper-selecting relay, the two sets of wipers hunting simultaneously.