Patent GB-767604-A (GB)
Title: Improvements relating to code communication systems suitable for centralised trafficcontrol of railways
IPC: B61L7/08
Filed: 1954-06-04
Abstract: 767,604. Centralized railway traffic control systems. GENERAL RAILWAY SIGNAL CO. June 4, 1954 [June 5, 1953], No. 16614/54. Class 105. [Also in Groups XXXVII and XXXVIII] In a remote control system such as a centralized railway traffic control system of the synchrostep type, i.e. one in which each station has a self-propelled timing device (see Group XXXVII) controlling a bank of stepping relays so as to be operated in synchronism at the sending and receiving stations to establish successive channel circuits for the transmission or reception of successive code elements, a source of energy is provided at each station with transmitting means for initially energizing the line circuit or other communication channel such as a line carrier channel or space radiation at a single carrier frequency, so as to create field station and control office starts by the simultaneous release of the timing devices or oscillators at all locations and for determining the character of successive code elements, to identify indication or control operating cycles, to constitute a station identification code and to represent the indications or controls to be transmitted. In the system to be described station identification for the transmission of controls thereto and indications therefrom is effected by respective station identification code response stick relays (station relay) initially energized at the beginning of each operating cycle and jointly controlled in accordance with the station identification code allocated to the station and as applied to the line circuit so as to be maintained energized, after the transmission of the station code elements, at one field location only, dependent upon the code sent from the control office or the relative code superiority of the station codes of a plurality of field stations wanting to transmit indications at the beginning of an indication cycle. The sending location is rendered effective to transmit, during a given step period defined by the associated oscillator, the character of a code element then prescribed by a transmitting device that was preset during the immediately preceding step period. An intermediate portion of each step period, a " message " or sampling period, is defined by " chopping " means operated by the associated oscillator, for actuation of the code responsive device belonging to that step period to condition the sending location apparatus to change the character of successive code elements, or the receiving location apparatus to respond to such code elements thereby eliminating any tendency to cause an unwanted operation of the means responding to the character of such code elements. Figs. 2A and 2B arranged side by side illustrate the apparatus at the control office with typical associated parts of the control board. Figs. 3A and 3B arranged side by side illustrate the apparatus at a typical field station with a diagrammatic representation of a simple track layout in the top right-hand corner of Fig. 3B. A pair of line wires 1 constitutes the communication channel between the control office and the field station. The distinctive character of a code element is determined by the energization, a mark code element or de-energization a space code element of this line circuit 1 during the stepping interval allocated to the element. A mark is employed at each station and control office for the automatic starting of the transmission of indications and controls. A battery B of positive polarity (+) and negative polarity (-) is used at each field station and the control office to energize the line circuit 1. The code elements, however, could be formed by controlling the energization of the line circuit with carrier frequency. The system is normally at rest or inactive and is automatically set into operation for transmission of controls by manipulation of the panel levers in the control office, or for transmission of indications by changes in the condition or position of the track switches, signals or track circuits, communication between the control office and the respective field stations being on a timesharing basis and the transmission of indications from the field stations being in accordance with a preference determined by the station having in its identity code the earliest occurring and longest uninterrupted succession of " mark " elements, the energization of the line circuit during a step period by virtue of these " mark " code elements acting to retire an inferior station or stations by releasing its station relay. To send a control, say to field station 1, the appropriate switch lever SML or signal lever SGL on the control board at the control office, Fig. 2A, is appropriately positioned followed by operation of the push-button 1-PB to establish a circuit from (+) bc 4 LCS (back contact 4 of master relay LCS), bus 5, button 1-PB, winding of relay 1-LC to (-). Relay 1-LC pulls up and is held over bc 6 VL in parallel with be 7 CS, wire 8, winding of master relay LCS, bc 9, 2-LC of panel 2, and similar contacts (not shown) of other panels, fc 10, 1-LC (front contact 10 of relay 1-LC) winding of this relay to (-). At bc 4 LCS on energization of relay LCS in this stick circuit, the energizing circuits of relays LC of all other panels are opened and at fc 4 LCS an indicating lamp LT is lighted indicating that the push button has been effective to energize a code-setting relay LC which closes a number of contacts to make the energization of a set of control buses CB dependent on the existing position of the control levers of the corresponding lever panel and also on the station code allocated to this lever panel by jumpers across (for marks) the terminals 1 M/S &c. and without jumpers for spaces. Assuming no field station is transmitting or is in the start condition to transmit indications, cycle selector relay CS is operated to designate a control cycle by closure of fc 78 LCS from (+) on bc 73 VI and over its upper winding and relay CS is maintained energized until the end of the control cycle over (+) &c 6 VL and its lower winding. At fc 80 CS circuits are prepared for even and odd transmission relays EMT, OMT, the relay EMT being energized by a channel circuit of the stepping bank. At fc 68 EMT line battery B is connected through oscillator contacts L2 across the line circuit 1 energizing the line relay LR at the control office and the lines relays such as 1-LR (Fig. 3A) at the field stations, which at bc 75 LR and bc 90, 1-LR &c. open the energizing circuits of the holding magnets OSM, 1-OSM &c. at all the locations, to release the respective oscillators which on swinging past the centre contact operating position measure equal periods of time and effect the sequential operation of the relays VI-VL. Since there are more indications or controls to transmit than relays in the bank the stepping bank of relays at each location is caused to repeat or partially repeat to different degrees its stepping cycle to provide the necessary number of transmission or reception channels, otherwise the operation of the stepping bank of relays is similar at all locations. Thus in the at-rest condition of the bank, all quick-acting relays V1-V5 and slow release relay VL are de-energized and as the oscillator swings for the first time through its centre position from left to right contacts R1, Fig. 2B, close before contacts L1 open to complete the relay V1 energizing circuit from (+), contacts R1, wire 48, bc 49 V4, bc 50 V2 upper winding of relay V1 to (-). Relay V1 pulls up and holds by a circuit for its lower winding over fc 51 V1 bc 53 V4 and bc 54 V5 in multiple and bc 55 VL. On the next half cycle of the oscillator as it swings back to the left, contacts R1 open and L1 close to complete an energizing circuit for the relay V2 over its lower winding and fc 58 V1, bc 57 V3 and wire 56. Relay V2 pulls up and holds by energization of its upper winding over fc 59 V2, bc 53 V4, bc 54 V5 and bc 55 VL, the operation continuing at each half cycle to operate in succession the other relays V3-V5, relay V1 holding until both relays V4 and V5 are operated. Relay V4 picked up by contacts L1 is held by its upper winding over the contacts R1 and fc 49 V4 and fc 62 V4 in series, so that contacts R1 are made to close before contacts L1 break. Relay V4 is held during period 5 when relay V5 is pulled up, over contacts R1, wire 48 and fc 49 V4 and held over fc 63 V5 and bc 55 VL. Relays V1, V2, V3 are now de-energized by the opening of bc 53 V4 and bc 54 V5. During the next oscillator swing contacts R1 open to release relay V4, its pick-up circuit through contacts L1 being open at bc 61 V5. During the next oscillator swing, the seventh stepping period, closure of contacts R1 energizes relay V1 for the second time and is held over bc 53 V4. Assuming three step periods for station selection and three for transmission of controls, a control cycle is completed upon the pulling up of relay V1 for the second time. During the next oscillator step, relay V2 pulls up and also relay VL over circuit (+), contacts L1, wire 56, bc 57 V3, fc 65 V1, fc 66 V5, fc 67 CS, f c 61 V5, winding VL to (-). At bc 55 VL relays V1 and V5 are released and at fc 61 V5 and fc 66 V5 relay VL is de-energized and after a time delay drops away to close its back contacts. At this stage the even transmitting relay EMT will be de-energized and relay LR also so that an energizing circuit for the oscillator magnet OSM exists from (+), bc 73 V1, bc 74 V5, bc 75 LR, winding OSM to (-) and the magnet is energized to hold the oscillator inactive. The holding circuit for relay EMT is open at fc 80 CS when relay CS was released at bc 6 VL, at the end of the control cycle. The relays EMT, OMT, whose energizing circuits are alternately prepared by the operational swing of the oscillator are energized to effect the energization of the line circuit 1 for even and odd periods respectively