Patent GB-691032-A (GB)
Title: Improvements in apparatus for use in railway traffic control systems
IPC: B61L7/08
Filed: 1947-08-05
Abstract: 691,032. Electric selective signalling. SIEMENS & GENERAL ELECTRIC RAILWAY SIGNAL CO., Ltd., and FIELD, R. W. G. Aug. 3, 1948 [Aug. 5, 1947], No. 21221/47. Class 40 (i). In a system wherein control codes may be sent from a central station to effect an operation at one or more outstations, and indication codes may be sent from any outstation to the central station to indicate a change of state of apparatus at an outstation, the timing relays for generating both control and indication codes are located at the central station. The invention is described as applied to a centralized traffic control system, where the line 12 is normally energized from a battery 11 at the central office Fig. 1, and all outstations, one only of which is shown in Fig. 2, are connected in series. The equipment shown is only that necessary for initiating an indication signal from an outstation and transmitting that portion of the office. The identifying portion of the signal consists of six forward impulses (i.e. normal direction of line current) each of which is followed by a reverse impulse or a space (line open) depending on the selective strapping of contacts 1, 2 ... 6 to the common line leading to a relay M, Fig. 2; operation of relay M during a forward pulse polarity. Contacts 1, 3, 6 are shown strapped for the station shown so that reverse impulses follow the first, third and sixth forward impulses, and spaces follow the remaining forward impulses. The duration of the pulses is determined by interacting timing relays LS, LFR, LT at the central office. At the office, line relay LF and relays LFR, LS. are normally energized, and at each station line relay LA and relay LAR are normally energized. Initiating an indication code. A change of state of apparatus at a station closes contacts S, Fig. 2 to energize relays M, P in turn. The stations more remote from the office are thereby disconnected from line at contacts P2 and the lefthand high resistance winding of relay M is shunted across the line to reduce the line current at the other stations. Normally operated line relays at the office and at all stations are thereby caused to relapse. At all outstations the release of the line relay LA, is followed by release of relay LAR and operation of relays BD, BB, F. Relays BB, BD remain up for the signal duration. Relays BB prevent initiation of an indication code from any other station until the first is completed, and relay F at the operative station checks that the office equipment responds correctly to the indication code transmitted, its locking circuit being broken if the response is incorrect. At the control station relay LFR also relapses whereupon a lagged relay BC operates, locks for the signal duration, and energizes the relay LT and a slow to operate relay ST. Relay LS releases as LT energizes to disconnect battery from the line whereupon relay M at the station releases and short circuits the line wires at M1. When relay ST pulls up, LT relapses, and LS reoperates to reconnect battery to line 12 to energize LF and all LA line relays in stations up to and including the operative substation. Indicating code transmission. At the office the energization of line relay LF (first forward impulse) is followed by that of relays LFR, SX. LS, LT, and at the operative and nearer outstations energization of line relay LA is followed by that of relays LAR, TX, IT. The next code step, in the example quoted, is a reverse impulse. This is determined by the strapping of contact 1, Fig. 2, which causes energization of relay M over contacts LARI, whereupon the line current is reduced as before causing the line relays LF, LA to relapse. At the office, as contacts LFI fall-off, a relay Z is energized in series with the right-hand winding of relay LFR which holds and relay Z locks over Z1, this operation occurring before LS has released in response to energization of LT following that of LFR. After a small interval relay LS releases, and Z being operated, the line current is reversed, whereupon relay M at the operative station relapses and the line reverse relays LR, LB operated over the short circuited line path via M1. At the office the relay A is now operated over LRI and locks over BC 4. Relay LFR releases after LS whereupon SY operates in series with SX. Relay LT releases and reoperates LS, when Z releases and restores.the line current to normal (second forward pulse). Line reverse relays LR; LB thereupon release and line forward relays LF, LA reoperate. At the office LFR reoperates and relay 2 S is operated and locks. SX releases. At the station, relay TY operates in series with TX as line relay LA releases at the end of the first forward impulse. As LA now operates for the second forward pulse, relay 2 T is operated and locks. LAR is operated and TX relapses. As code terminal 2 is not strapped, relay M cannot be operated and the second forward impulse persists until the office relay LS releases in response to energization of LT. As relay Z is not now operated the second forward impulse is followed by a space (line open) which causes release of line relays LF, LA. At the control station LFR released by LF, releases SY, LT. At the station LAR and TY release after LA. Impulsing now proceeds as above described, the respective station and office relays 3 T, 3 S, 4 T, 4 S ... 6 T, 6 S being operated during the third, fourth... &c. forward impulses. A reverse pulse follows the third and sixth forward pulses as operation of relay M over the strapped contacts 3, 6 associated therewith, during the preceding forward pulses, energizes Z. The reverse impulses, only, operate indicator relays of the series A, ... E, F N at the office over contacts LRI. Thus in the example quoted relays A, C, F N are operated and locked and light lamp 32, as F N operates, to identify the operative station. When the final reverse impulse ends the forward line relays LF, LA operate, LFR operates office relay RL causing all office relay to revert to normal. At the operative station the continued energization of line relay LA releases the lagged relay BD to restore the circuits to normal. The change in the position of equipment at the operative outstation may now be signalled by the same system, the strapping of further contacts such as 1, ... 6, for controlling the indicator code being, in this case effected by relay contacts operated by the change of state.