Patent GB-727613-A (GB)
Title: Improvements in electrical systems of remote supervision and/or control
IPC: B61L7/08
Filed: 1952-12-22
Abstract: 727,613. Electric selective signalling. SIEMENS & GENERAL ELECTRIC RAILWAY SIGNAL CO., Ltd., and FIELD, R. W. G. Dec. 22, 1952, No. 32423/52. Class 40 (1). Apparatus at an outstation is arranged in groups and a change of state of a piece of apparatus is signalled to a central station by initiating a signal impulse train, generated at the central station, and having a group identifying portion and another portion for identifying the apparatus within the group. General operation. Fig. 3. A change of state at an outstation causes the normal line current to be reduced. This initiates the synchronous stepping of relay counting chains at the central station and at the operative outstation while " forward " current pulses are being sent to line from the central station. In the successive positions of the counting chains the apparatus groups are first sensed in succession, and then the pieces of apparatus in the operative group. When the operative group and those pieces of apparatus within this group which are in the " on " position for example, are sensed, they cause a reduction in the corresponding line eurrent pulse followed by a reverse current line pulse. The other forward pulses are followed by line breaks, i.e. zero line current. The reverse-current line pulses operate relays at corresponding positions in an indicator relay chain at the central station, which, at the end of the signal cycle, light lamps to indicate the positions of all those pieces of apparatus within the group concerned which are in the " on " position, this indication remaining until initiation of the next signal cycle. The arrangement described will indicate apparatus positions only for one group at a time, i.e. for that group in which a change of state has occurred, but changes of state in both groups may, it is stated, be signalled by sequential signalling trains. Where a plurality of outstations is connected party-line fashion to the central station, a station identifying code signal is first sent, e.g. as described in Specification 691,032. This is not described in the present Specification. Initiating an indicating signal. Fig. 2 shows one outstation having two groups A, B, each catering for five pieces of apparatus. Upon a change of state of any one of these, the switch R1 ... R10 corresponding to the operative apparatus piece is reversed. In addition a group indicating contact ST1 or ST2 corresponding to the operative group, and a start contact STA are closed momentarily, it being arranged that a change of state does not occur in both groups at the same time. The transmission line L1-L2 is normally energized from a battery at the central station, Fig. 1, and the " forward current " line relays LA at all outstations are energized. Assuming, e.g., that switch R3 in group A, Fig. 2, has been closed, then group contact ST1 will also have been closed. Over the start contacts STA a relay M is energized which in turn operates a relay P. Relay P disconnects line L3-L4 leading to more remote outstations at contacts p2, and reduces the forward current in line L1-L3 by connecting the high resistance left-hand locking winding of relay M in series with the line. The " forward " line relays LA at the operative and at all intermediate outstations are thereby released, and in turn release normally-operated relays LR, Fig. 2, which energize slow-to-release relays BB. At the operative outstation only, relay BB locks relays P, TA, relay TA having been energized by key ST1. Central station operation, Fig. 1. The reduction in line current as relays M, P, Fig. 2, operate, causes normally-operated " forward " line relay LF to relapse, which in turn de-energizes a relay H and energizes a delayed release relay BC, which locks, energizes a slow-to-operate relay ST, and also a relay LT which releases a normally-operated relay LS to break the line current at LS1-LS2, thus releasing relay M, Fig. 2. When ST pulls up it operates a relay J slowly, releases LT and operates HA. Relay LT re-operates LS to apply full forward current to the line, thereby re-operating the forward line relays. Relay H is re-operated by line relay LF. It operates the first relay 1S of a counting relay chain 1S-8S, operates a relay SX and reoperates LT which de-energizes LS. Since, however, group A relay TA is operated at the operative outstation, Fig. 2, the relay M is re-operated to reduce the forward line current before LS releases,. so that line relay LF releases before LS to operate a relay Z. Thus when LS releases, reverse current flows in the line over contacts z2-z3, Fig. 1, to operate reverse line relays LR, Fig. 1, and LB, Fig. 2. Relay LR, Fig. 1, operates indicator relay A and releases H whereupon a relay SY operates in series with SX and LT is released to operate LS which reapplies forward current to the line. Reverse line relay LR releases and LF operates since relay M, Fig. 2, has been de-energized by this time. Relay LF releases Z and operates H which operates relay 2S in the counting chain. Relay H releases SX and re-operates LT. As group relay TB, Fig. 2, is unoperated, relay M is not inserted in the line during the forward current line pulse so that when LS releases upon operation of LT, the line circuit is broken as relay Z is not operated. Forward current pulsing continues in this way synchronously with the stepping of the counting chain 1S-8S under control of relay SX, SY, H, until the closed contact R3, Fig. 2, is sensed during the fifth forward pulse when the line current is again reduced by operation of relay M to cause a reverse line pulse to follow the forward pulse and operate indicator relay E of the indicator relay chain A-FN. Subsequent forward line pulses are followed by breaks in the line until the last (stop) forward impulse, when the line current is again reduced, the following reverse line pulse operating the indicator relay FN. The relay FN lights the indicator lamp S3 over contacts of the operated indicator relays A, E to indicate the operative apparatus R3 and the remaining relays revert to normal ready for the next indication signal, when the energization of relay ST resets the indicator relays. It will thus be seen that the operated relays of the indicator chain A ... G correspond to the operative group A or B and the closed switches R1-R5 or R6-R10 within the operative group. Clearly only one group relay can function at a time but a plurality of changes of state within the operative group may be transmitted during one signal impulse train. Outstation operations. The operative group relay, TA in the above-mentioned example, connects the apparatus contacts R1-R5 to relay M. When the first break in the line current occurs, M releases, and when the full forward line current is restored, LA pulls up and operates LR, Fig. 2, which operates a relay TX and relay 1T in the counting chain 1T ... 8T. The relay M is again energized over contacts 1T3 to reduce the line current and cause a reverse line pulse to follow. This operates a " reverse " line relay LB which has no effect but would be used for control operations initiated from the control station. The forward line relay LA relapses to release LR, Fig. 2, when a relay TY operates in series with TX so that when the next forward line pulse occurs the counting chain relay 2T operates. In this way the counting relay chain 1T-8T is stepped by the forward line pulses under the control of relays LR, TY in step with the relay chain 1S-8S at the central station, and at successive steps, the contacts TA2, TB2, R1-5 are sensed. Since only TA2 and R3 are closed, in the example quoted, the relay M is energized to reduce the forward line current and cause a reverse line pulse to follow the corresponding forward pulses and operate the indicator relays as above described. During the last forward pulse the relay M is energized over TY3 to cause operation of indicator relay FN at the central station, after which all relays revert to normal.