GB534866A - Improvements relating to telephone and like signalling systems - Google Patents

Abstract

534,866. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., CLAY, D. L., and BARTLETT, C. J. C. Oct. 16, 1939, No. 27986. [Class 40 (iv)] In an impulse repeater, the first impulse of each train is suppressed, an additional impulse being sent at the end of each digit received. In the arrangement shown in Fig. 3, line relay A which bridges the outgoing junction is followed by release relay B, metering relay J and a relay HA. On its first relapse in response to a dialled digit, A energizes a relay X and dialling relay C but does not repeat the impulse since the impulse contact is shunted at b4, y4. At the end of the impulse Y is energized so that subsequent impulses, if of normal duration, are repeated in the ordinary way, relays X and Y holding throughout the digit on account of their short-circuited left-hand windings. If the make periods are too long X falls back during each to shorten them as far as the repeated impulses are concerned. The character of the repeated impulses is further improved by a spark-quenching circuit across the impulse contacts. At the end of the received digit relays X, Y, C fall in turn and a further impulse is then sent over the junction. The reply signal energizes D whereupon MD pulls up sluggishly to apply a booster impulse to the test wire and is released to terminate the impulse. MD also energizes reversing relay DD. During release the relapse of B initiates the release of the local switches and the temporary re-operation of C guards the repeater for a further period to allow the release of the switches ahead. In a modification, Fig. 2 (not shown), a similar arrangement is provided in a repeater in which the impulses are repeated as bursts of voicefrequency current. In this case two high speed relays of the kind described in Specification 405,436, [Group XXXVII], connected in series act as the impulse relay and the relay Y has two helping relays of the high speed type which ensure proper functioning of the circuit of the "make" part if the incoming impulses is shorter than the operating time of Y.