Patent GB-775353-A (GB)
Title: Improvements in and relating to electric signalling systems
IPC: B61L7/08
Filed: 1952-07-29
Abstract: 775,353. Electric selective signalling systems. SIEMENS & GENERAL ELECTRIC RAILWAY SIGNAL CO., Ltd., AUSTIN, T. D., and RIDDLE, H. J. N. July 29, 1953 [July 29, 1952], No. 19151/52. Class 40 (1). [Also in Group XXX] A receiver mechanism responsive to an electric impulse code signal such as used on railway track circuit signalling installations for effecting control over traffic or track controlling apparatus in accordance with the particular code identified, for example at frequencies of 75, 120, 180 impulses per minute corresponding to three different signal aspects includes a group of relays arranged to count the number of impulses received in a predetermined period of time initiated by the first impulse of the code and to take up one of a number of conditions dependent on the count which condition is used to effect the desired control. A timing circuit set into operation by the initial impulse is used to interrupt a train of counting relays at a moment-determined by the timing circuit, their condition at that moment being indicative of the impulse code. In the embodiment shown a train of relays ACR-GCR operate in succession and cut out the preceding operated relay upon repeated reversals of the contact CFR1 of a code following relay (not shown) and of a relay X. Assuming slow release relay LTB is in its picked up condition, front contact (f.c.) LTB1 is closed and on first closure of f.c. CFR1 on receipt of the first impulse of the code relay ACR is picked up over its upper windings over b.c. (back contact) BCR4 &c. and is held over its lower winding and f.c. ACR1 and b.c. BCR1 and f.c. LTB1. At the end of the first impulse relay X is picked up over its upper winding, f.c. ACR2 and b.c. CFR1. On receipt of the second impulse relay BCR is picked up over f.c. CFR1, f.c. X1, f.c. ACR3 and releases relay ACR at b.c. BCR1. During this action relay X is held by current over resistance RX but is released by energization of its release lower winding over f.c. BCR3 when relay BCR is picked up. Relay CCR is then picked up over b.c. X1 f.c. BCR5 on receipt of the next impulse, releasing relay BCR at b.c. CCR1, and so the counting action proceeds, the pick-up circuit of relay ACR being opened by a contact BCR4 &c. of each other counting relay. On operation of relay ACR, the timing circuit as described in Specification 621,636, [Group XL (c)], is set into operation at f.c. ACR4 to energize relay LTA which releases in due course followed by relay LTB which at f.c. LTB1 opens the holding circuits of the counting relays and stops the counting action. One or other of the front contacts BCR6-GCR5 will be made and at b.c. LTA2 when relay LTA releases a controlling impulse will be transmitted to the apparatus to be controlled, e.g. a signal relay. In a second embodiment described the counting unit comprises a number of individual counter circuits utilizing the charges on transfer condensers to charge a capacitor controlling the flow of anode current in the release winding of a relay such as relay LTA, a front contact of which is included in the controlling circuit of e.g. the signal relay. The Provisional Specification contains description of two further code impulse receivers not falling within the invention claimed, each being for use with a code synchronizing characteristic instead of the timing device as in the invention claimed. The first of these receivers receives alternately short and long impulses, the first of which impulses functionas a synchronizing impulse and comprises a train of relays alternate ones of which are operated by the short and long impulses respectively, a back contact of the code following relay, when open during the long impulses, causing a slow release relay to drop away to effect circuit changes which route the long pulses to the relevant operational relay. The second of the receivers is controlled by a long space in the received code as a synchronizing feature, a slow release relay picked up by the impulses, being released during the long space period to release all the relays of the train of relays to the " at rest " condition. Specification 766,871 also is referred to.