Patent GB-796165-A (GB)
Title: Improvements relating to remote control systems
IPC: B61L7/08
Filed: 1955-08-04
Abstract: 796,165. Electric selective signalling systems. WESTINGHOUSE AIR BRAKE CO. Aug. 4, 1955 [Aug. 10, 1954], No. 22422/55. Class 40 (1). A remote control system, e.g. for centralized railway traffic control, employing codes of long and short elements which are transmitted one at a time over a single channel, at least a portion of which is a direct current line circuit, between a control office and a number of field stations, as in the system described in Specification 589,332, is provided with means at the control office whereby the stalling of a code causes the operation of the control office line relay and all the field station line relays to their reverse position, or their maintenance in that position, for a predetermined period of time, followed by their substantially simultaneous operation to their normal position whereby the coding apparatus at the control office and at each field station is re-set automatically to its at-rest position. The invention is described as applied to the system disclosed in Specification 754,181, and may use either coded direct current pulses, or coded high-frequency current pulses. General lay-out. Fig. 1 shows the office and one field station line circuit connections using direct current pulses. Line Y is normally connected to the positive terminal and line Z to the negative terminal of office line battery 31 via back contacts of b, c, of office line polechanging relay PC and back contacts b, c, of office first transmitter relay OIT. The line circuit includes the primary windings of an impulse transformer RT whereby the office line relay OR is controlled when receiving indication codes. Control codes are transmitted from the office by periodically opening and closing the line circuit through contacts b, c, of relay OIT. At the field station the line relay R, which is a biased relay, is normally energized as shown via back contacts a and b of master relay M, and is operated by the pulses of a control code between its normal and reverse positions. Relay R controls the station line coding unit as described in Specification 754,181. Indication codes are transmitted from the station by the operation of a first transmitter relay IT which shunts and closes the line circuit through relay R alternately. Relay M is operated at the, beginning of the code to pole-change the line circuit connections, and shortly after, one of the timing relays LBP picks up so that relay IT may perform the coding operation. At the office the twoposition stick relay OR is operated through transformer RT by the periodic shunting and closing of the line circuit by IT, alternately between its normal and reverse positions to control the office line coding unit. During control codes from the office, OM is energized to short the secondary of transformer RT, and OR is operated between its two positions over contacts d of OM and O1T by battery 32. Fig. 2 shows a system using high-frequency current pulses between the office and a remote line station over lines L1, L2 with a direct current circuit over lines Y, Z, extending beyond to the field stations. Control codes are transmitted from the office by oscillator No. 1 at one frequency to the receiver No. 1 at the remote line station, oscillator No. 2 at a second frequency and receiver No. 2 providing a corresponding link in the opposite direction for the indication codes. Each oscillator is normally suppressed, at the office by contact a of relay TC, and at the remote station by contact a of relay RL. During coding operation of relay OIT, TC is correspondingly operated between its normal and reverse position. At the end of an indication code TC is energized through the operation of a code stopping relay OCS to transmit a re-set pulse. Pulses produced by the operation of TC correspondingly operate relay C at the remote station, relay C being normally de-energized, each pulse causing the opening of the remote line circuit Y, Z to form the control code. Indication codes from any of the field stations are received by relay RL through transformer RLT to cause pulses to be transmitted from oscillator No. 2 to the office. Relay RL is also controlled by a remote line unit (indicated by a dot-dash square) which provides for pole-changing the remote direct current line circuit during indication codes, stabilizing relay RL during control codes, and restoring normal polarity to the direct current line circuit at the end of an indication code, even though no re-set pulse is received. Pulses from the remote station received at the office operate relay OC between its normal and reverse position this causing OR to be similarly operated between its reverse and normal positions to cause the office line coding unit to receive the code in known manner. Transmission and reception of indication and control codes. Figs. 3a and 3b show the office line coding unit connections for a direct current line, but the connections could be arranged, as in Fig. 2, for A.C. working. The coding action is initiated by closing the " start " contact 50, Fig. 3b, which energizes master relay OM, which remains picked up during the entire coding action, and thus completes a, circuit for O1T. O1T picks up and completes a circuit for O2T which then picks up. When. O1T picks up relay OR is operated to its reverse position to activate the timing chain relays OIL, O2L, OLP, OLB, OLBP, and the counting chain relays O1 to 08. Relay O1T is alternately picked up and released to produce short code steps, by back contacts of the odd numbered counting chain relays O connected in series, the long odd numbered code steps being produced by holding O1T picked up by stick circuits. Once released O1T cannot pick up until O2T releases, the timing of even numbered code steps being determined by release of O2T, which is held by stick circuits similar to those for O1T to produce long evennumbered code steps. The desired coding is selected by the manually set station selection and function control circuits (not shown). Relay OR operates alternately to its reverse and normal positions each time O1T picks up and releases, and steps along the counting chain relays and influences the operation of the timing chain relays, which have slow release characteristics, O1L and O2L remaining picked up for the duration of short code pulses, O1L releasing during odd numbered long code steps, O2L releasing during even-numbered long code steps, and OLB and OLBP remaining picked up for the duration of a code. When relay 08 in the counting chain is energized, a chainrepeating relay OCR is energized to establish circuits to re-use the counting chain relays O1 to 07, and the code stopping relay OCS is energized on the last selected step of the code, which must be an even-numbered step, to return the coding unit to its at-rest condition, The initial code pulse from a field station energizes the top winding of relay OR which operates to its reverse position when either a D.C. or A.C. circuit is in use. Closing of the reverse contacts of OR initiates the timing chain and counting chain operation and energizes the line pole-changing relay PC to lock out all field stations except the one transmitting, and also momentarily shunt the secondary of transformer RT. When PC picks up, relay PCP is energized and breaks this shunt. OR is held in its reversed position over its lower winding. If an A.C. circuit is in use the pick up of PC connects relay TC, Fig. 2, to the front contact b of OCS. Relay OR follows the code transmitted from the field station, and during the final code step OCS is operated to release PC and restore the line circuit to its normal polarity, release PCP, restore OR to its normal position and return the coding unit to its atrest position. Fault conditions. In the case of a fault in the coding equipment or the communication channel, the system ensures that all the station line relays R and the office line relay OR are in their reverse position and that the timing relays have had time to re-set in this condition. The line relays are then returned to normal substantially simultaneously and the timing relays allowed to re-set at the same time in the office and stations. This synchronizes the various coding units and conditions them for further action. Control code halted on odd-numbered step due to a fault. Relay O1T is held energized and holds OR in its reversed position, and the timing relays O1L, OLB, OLBP, release but O2L remains picked up. Release of OLBP de-energizes OM and opens and re-sets the counting and selecting relay circuits. Release of OM causes PC to pick up which in turn energizes PCP, and O1T is de-energized but remains up for a period of time during which the D.C. line circuit is open. If an A.C. circuit is in use relay TC remains energized during the time O1T holds up whereby at each station line relay R remains in its reversed position and the timing relays (not shown) release in the same order as at the office, 2L, which corresponds with O2L at the office, remaining energized. The release of relay LBP at each station opens the counting and selecting relay circuits to prevent further reception of any code. A similar action takes place when a D.C. circuit is used. When PC and PCP pick up, relay OR operates to normal and the release of O1T closes the D.C. line circuit but the line relays do not respond as the polarity of the line current is reversed by PC. In the A.C. system TC remains energized via an alternative circuit. With OR in its normal position the office timing relay chain is re-energized, PC and PCP release, and the timing relays release in the normal order. The line current in the D.C. system is restored to normal polarity, and the station line relays return to their normal position. In the A.C. system, TC is released and the line relays return to normal. Control code terminated on an even-numbered step prior to the last step due to a fault. Relay O1T fails to pick up and relay OR is