Patent GB-425925-A (GB)
Title: Improvements in communication systems more particularly for centralised traffic control installations
IPC: B61L7/08
Filed: 1933-11-29
Abstract: 425,925. Electric selective signalling and remote-control systems. GENERAL RAILWAY SIGNAL CO., Rochester, New York, U.S.A.-(Assignees of Preston, N. D.; 287, Aberdeen Street, and Bushnell, C. S.; 53, Hancock Street, both in Rochester, New York, U.S.A.) Nov. 29, 1933, No. 33514. Convention date, Nov. 30, 1932. [Class 40 (i)] In a selective signalling and remote control system in which signals and controls are transmitted by codes of impulses, the impulses transmitted in one direction, e.g. for control, are coded in respect of one characteristic such as polarity whilst the impulses transmitted in the opposite direction, e.g. for supervisory signals, are coded in respect of the duration of the makes and breaks so that transmissions in the two directions may take place simultaneously. The invention is described as applied to a railway signalling and control system in which remote units, such as points, are operated by the transmission of a code comprising a constant number of positive and negative impulses whilst supervisory signals are transmitted back from the remote point by the same number of impulses, the code comprising the lengths of the makes and breaks in the signal code. Duplex working is provided and as both the make and break periods are used in the supervisory codes, two supervisory codes are available for each control code. Relays are used for producing, counting and timing the impulses. Specifications 377,971 and 419,401 are referred to. Production and transmission of control code. The control station equipment is indicated in Fig. 1, the individual apparatus for controlling the remote point TS<1> (Fig. 2) only being shown. The control lever SML is placed into the relative position for the remote control required and the start key SB is pressed. The relative relay CD picks up in a manner described in Specification 377,971 and STR is energized and locks over back contact 13 of VP. Relay PC is released and NC is operated to reverse the current flow over the line circuit 7, 9. Relays F, FP, SA and SAP at the control office and the corresponding relays F<1>, FP<1>, SA<1>, SAP<1>, &c. at the remote stations are energized. Relays E and EPT pick up and then EP falls away slowly. When EP has released PL is actuated to open the line circuit and terminate the first pulse which is always a negative pulse of long duration. Relays F and FP release and VP pulls up and locks via a back contact of IV. The control jumpers 44, 48, 49 are wired to determine the code to be transmitted and jumper 44 is now effective to operate PC over bus 46. Relay NC released when VP pulled up. Relay E is also de-energized when VP actuated so that EP is re-energized and PL falls away to recomplete the line circuit and, as PC is up, a positive pulse is transmitted to the remote stations. F and FP pull up, relay 1V energizes and locks and then E is actuated allowing EP to again fall away and terminate the first control pulse. VP falls away, PC releases NC is operated over 48 and 50 and E falls away allowing EP to pick up and PL to again complete the signal line. As NC is now energized, this second control pulse is negative. F and FP again pull up, 2V is energized and locks and E re-energizes to initiate the termination of the pulse as before described. VP is re-energized when FP falls away and holds during the next pulse and wiper 49 becomes effective to energize PC for the third control pulse. A code of three long pulses positive, negative, positive is thus transmitted after the long initiating negative pulse and this is effective, as will be described later, to select relay SMR<1>, Fig. 2. Relay 3V energizes during the third pulse and VP again releases at the end of the pulse so that bus 54 becomes energized and SML is effective to energize either PC or NC for the control signal which is either a positive or a negative pulse. Relay LV pulls up during this pulse and VP releases at the end of it so that E is held energized and PL remains up for a long period. Relay SAP falls away during this prolonged break releasing the counting relays 1V-LV and relay E falls away. EP re-energizes and PL recompletes the line circuit which is now in its normal condition. Reception of control code. The signalling line 7, 9 is normally continuous through all substations as shown and the line relays F<1>, F<2>, &c. are normally energized to their right hand positions. When the long initiating negative pulse is received the line relays all move to their left hand contacts and, as shown for a typical substation in Fig. 2, relays FP<1>, SA<1> and SAP<1> pull up. During the first break VP<1> is energized and locks to a back contact of 1V<1>. The relays 1V<1>, 2V<1>, 3V<1> and LV<1> pick up during the impulse train as described above for relays 1V &c. and VP<1> follows the movements of VP (Fig. 1). As a result, the relays 1ST<1>, 2ST<1>, 3ST<1> are connected in turn to contact 135 of relay F<1> and these relays are positioned in accordance with the polarity of the pulses received. As the code transmitted for the jumpers 44, 48, 49 connected as shown in Fig. 1 is +, -, + the armatures of relays 1ST<1>, 2ST<1>, 3ST<1> are set as shown in the Figure so that when the fourth control pulse is received, relay SMR<1> is operated either over its upper or lower winding from contact 135 and sets its armature to drive SM<1> to operate points TS<1> in the required direction. When the final long break is received SAP<1> falls away and the apparatus restores to normal. Transmission of supervisory code. As an example of the transmission of a supervisory code, it is assumed that a change occurs in the track section shown so that relay T<1> is de-energized. During the time contact 153 is passing from its front to its back position, the normally energized relay CH<1> falls away so that if, or when, the apparatus is normal PL<1> energizes and locks, opening the line circuit at 125. The line relays F, F<1>, F<2>, &c. at all stations release, preventing the operation of relays such as PL<1> at other stations and, at the main station, energizing STR. Relay STR locks and initiates transmission of an impulse cycle, but as no CD relay is up, relay PC cannot be energized. Relay NC is, however, held throughout the cycle so that a code of negative pulses only is transmitted. This code is reserved for supervisory calls and is not allotted to a field station. At the field station relay PLT<1> is energized over 135 in its central position, and closes at 163, the line circuit through LO<1>. Relays F and F<1> energize and the system advances to the conditioning period as before described in which SA, SAP, E, EPT and P2 are picked up and EP is released. At the field station CHP<1> is released and when F<1> moves to the left during the conditioning period, FP<1>, SA<1> and SAP<1> are picked up and LO<1> is locked. CH<1> is reset and PL<1> released to reclose the line through the remaining stations. The apparatus at the control station now transmits an impulse cycle of negative impulses, the relays 1V, 2V, 3V, &c. at the main station and the corresponding relays at the substations operating in the same manner as described above. During the normal control cycle the periods during which the line is completed are normally long, whilst the breaks are normally short. These periods are modified by the equipment at the transmitting field station and in the example shown the code is first " off " period short, second " off " period long, first " on " period long, second " on " period short, and for this purpose buses 173, 174 are left open and buses 175, 176 are connected to positive. The wire 177 is connected to positive through contact 178 of relay T<1> and the length of the third " on " period is thus determined by the condition of T<1>. If an " off " pulse is to be long the relative bus connected to positive is extended to PL<1> and this relay energizes and opens the line circuit at 125. As 1V<1> is at this stage up, the loop through LO<1> is open so that when PL at the control station recompletes the loop at the end of a normal short " off " period, the line relay F remains de-energized due to the open circuit at the field station. Relay PL<1> opens the circuit of PCT<1> and when this relay releases after a comparatively long period, PL<1> falls away to reclose the loop. Similarly, if an " on " period is to be short, when the relative bus is connected, PL<1> energizes to open the loop and terminate the " on " period after a very short interval. When long " on " periods or short " off periods are required, the field station equipment does not operate and the impulses are of the normal lengths controlled by the control office. Receipt of indication code. As the first " off " period was normally short, it terminated when E had released and EP had energized. When F re-energized on the first " on " pulse, relay 1PF was energized from 72 in its upper position so that 1PF moved its armature to the left as shown. The first " on " period is normal, that is long, so that it is measured by the release of EP and when F releases at the end of the period, relay 1PB is energized to move its armature to its left hand position, the circuit including back contact 78 of EP. This third period (second " off ") is made long, its length being controlled as described above, by PLT<1> at the field station. When E released during this period, F did not re-energize quickly enough to hold EPT so that this relay fell away. When this " off " period terminated, a circuit was completed from back contact 72 of EPT to energize 2PF to move its armature to its right hand position. Similarly, as the second " on" period is shortened, relay EP does not fall away and when the line is again opened relay 2PB is set to move its armature to its right hand position, the circuit including front contact 78 of EP. The third " on " period is controlled by the condition of relay T<1>. If T<1> is in the condition shown, relay PL<1> will n