GB703716A - Improvements in or relating to circuit arrangement for impulse control in telephone installations - Google Patents

Abstract

703,716. Automatic exchange systems. SIEMENS & HALSKE' AKT.-GES. May 31, 1951, No. 12948/51. Class 40 (4) A two-way repeater for conversion of A.C. to D.C. signals and vice-versa is so arranged that when in non-transmitting condition it can receive backward signals of one type while if the repeater is in transmitting condition it can receive backward signals of another type and pass on these signals after the transmitting condition has ended. Relay A1 in a repeater œK follows A.C. impulses on a trunk line VL and repeats them as D.C. impulses to operate relay A3 in a line selector LW. During a train of impulses, relay VI holds up and connects winding I of E2 to the b-wire. At the end of the train when VI falls back the repeater can receive rearward impulses. Loop impulses, such as answering, clearing and flashing, sent back by line selector LW operate E1 and therefore S which transmits A.C. impulses back over trunk line VL. Alternatively a leg impulse over the b-wire, such as the end-of-selection signal, produced by the energization of slow-release relays U (not shown) and V, operates E2 while the repeater is still in' transmitting condition. When VI falls back, E2 releases, returning the end-of-selection signal during its release time by operating S. In the modification of Fig. 2, E1 has two windings which are disconnected from the loop when the repeater is not in forwardtransmitting condition, but winding II of E1 responding to a commencement-of-conversation signal on the b-wire when contact z closes. E1 then operates S to return A.C. impulses to VL, the impulses ending when E2 and U1 fall back slowly. In Fig 3, an incoming repeater œK and an outgoing repeater œg reconnect the loop reception relay E1 in the event of a disturbance. Relay A1 receives A.C. impulses and send on D.C. impulses to A3 in the outgoing repeater, which sends on A.C. impulses. In œK, V1 holds up during a train of impulses and connects reception relay E2 to the b-wire but E2 does not operate. Rearward impulses from œg energize E3 but VI has meanwhile fallen back so that E2 still remains normal. In the event of a disturbance, however, during backtransmission, such as re-dialling coinciding with the end-of-selection signal so that E3 is energized when V1 responds to the disturbance, relays E2 and AB pull up, E3 being maintained over winding II until the disturbance ceases when VI falls back. E2 energizes U1 and S, the latter returning busy tone to the calling subscriber. VI, E2, E3 and AB then release, the last very slowly. E3 operates E1 which releases U1. E1 maintains S to continue the engaged signal until AB relapses when E1 and S fall back.