Patent GB-717142-A (GB)
Title: Improvements in or relating to code communication systems
IPC: B61L7/08
Filed: 1952-01-09
Abstract: 717,142. Centralized traffic control systems. GENERAL RAILWAY SIGNAL CO. Jan. 9, 1952, [Jan. 23, 1951; Aug. 3, 1951.] No. 708/52. Class 105. In a centralized traffic control communication system for railroads sequential code elements are transmitted in accordance with the actuation of the control devices or the condition of the points and/or signals and track circuits and a local oscillating pendulum type timing device at each station operates sequentially relays of a stepping bank associated therewith at equal intervals of time to establish successive channel circuits for the transmission or reception of successive code elements, the timing device at each station when transmitting being set into operation upon initiation of transmission from that station and when receiving upon reception of a controlling influence from the other station. Preferably a line circuit, e.g. a line used for other purposes but used as a carrier circuit for the present system exists between the control and field stations. The successive channel circuits being established through the line circuit but a radio link could also be used. At each station one oscillating pendulum type timing device or code oscillator and one stepping bank of relays is provided for transmitting and receiving the codes the indication codes being transmitted at a different time from the control codes. The control office transmitter takes precedence over the field station transmitter when both stations are simultaneously conditioned tp transmit the field station's start being locked out and the apparatus at that station conditioned for the reception of the control code. To this end the first element of a control code is a "mark" and the first element of an indication code is a "space," the said mark being effective to change the field station start to condition for reception. After completion of the reception cycle a subsequent cycle of operations is initiated for the transmission of the indication codes. The stepping relay bank at each station during each control cycle partially repeats the stepping cycle and during each indication cycle it fully repeats and partially repeats the stepping cycle to provide the requisite greater number of channels with only four relays in a bank. An arrangement of decoding relay contacts at the field station provides a parity check to prevent the execution of a garbled code. The timing device for governing the stepping of the relay bank is the torsional pendulum described in Specification 684,065, [Group XXXVII]. When the torsional pendulum is at rest an armature thereof is maintained in its extreme off neutral position against a magnetic stop which is energized by a winding CT so that it can be started from a predetermined contacting position on initiation of stepping of code communication apparatus at the associated station by interrupting the energizing circuit of the magnetizing windings CT. The oscillator operates electrical contacts only as it swings through its neutral position. Figs. 1A and 1B illustrate respectively the transmitting and receiving apparatus of a code communication system for the transmission of points and signal controls from a control office, Fig. 1A, to a single field location. Fig. 1B and Figs. 1C and iD illustrate respectively the additional apparatus at the control office and at the field station for transmitting indications from the field to the control office. The railway system illustrated consists of a main single track 20, Fig. 1B, having a second track 21 connected thereto by points 4W which is operated by a switch machine 4SM. Eastbound traffic over the points 4W is governed by the signal 2, while westbound traffic over the points 4W is governed by the signals 3A and 3B. The symbols (+) and ( -) indicate connections to the respective positive and negative terminals of suitable sources of direct current, and the symbols (B+) and (B - ) indicate connections to respective positive and negative terminals of a suitable source of direct current having a centre tap (CN). The prefixes f and b indicate respectively front and back contacts. At the control office, Fig. 1A, a two position points lever 4SML controls the points 4W and a three position signal lever 2-3SGL controls the signals governing traffic through the points 4W. The left and right hand positions of the lever 4SML are used for bringing the points 4W to its normal and reverse positions respectively. The centre position of lever 2-3SGL is used for putting 'the associated signals to stop; its lefthand and right-hand positions are used for clearing a signal for westbound and eastbound traffic respectively. The control office transmission apparatus contains relays CH and LC which are provided for each device such as the points or for each pair of opposing signals as such, 3A, 3B, that are to be distinctively controlled from the control office and these relays are used for the control office in the storing of designated controls for transmission and in permitting but one control to be transmitted at a time. Thus relays 4CH and 4LC are associated with the points lever 4SML and relays 2-3CH and 2-3LC are associated with signal lever 2-3SGL. Relay LCS prevents the interruption of a cycle of operations by the designation of controls for transmission at a time when prior designated controls are being transmitted. Relay CS assists in setting the receiving apparatus into operation and in the control of an associated repeater relay CSP upon the reception of indications. A similar group of relays is provided for at the field station. Relay C at the control office like relay C1 at the field station is a code transmitter relay which is effective to pulse the line circuit in accordance with each particular code selected for transmission. Relays 1V-4V comprise the stepping relay bank controlled by the timing device or oscillator CT. Decoding relays M, Fig. 1B, at the field station store the respective "mark" characters received until such time as the code is complete and execution of the control can be effected. Relays OM and EM, Fig. 1C, at the control office are energized when "marks" are received as respective odd and even numbered characters of the indication codes. Relays CP, and CPP at the control office and relay CP1, Fig. 1D, at the field station govern repeat of the complete operation of the stepping relay banks. At the field station magnetic stick relay WZ, Fig. 1B, controls the power track switch 4W; relays LGZ and RGZ are neutral relays with stick windings energized for stick signal control. Relays B, e.g. relay 2-3B controls the signals 2-3 to stop in accordance with the reception of a stop-code from the control office. Relays RM and LM, Fig. 1D are signal repeater relays and relay TR a track relay. At the control office, Fig. 1C, relays RMK, LMK; and TK are operated in response to specific indication codes received from the field station and govern indicator lamps RME, LME and TE. In the system shown the relays 2-3CH, 4CH, L, C, CS and the bank of relays 1V-4V at the control office, Fig. 1A, are normally energized when the system is at rest. The stick circuits for relay 2-3CH is over its contact f62, and arm 63 of lever 2-3SGL in its central position. The stick circuit for relay 4CH is over its contact f60, and arm 61 of lever 4SML in its left-hand position. Line relay L is energized from positive terminal of line battery LB, f90 of relay C, f91 of relay CS wire 89, relay L1 at field station, f92 of normally energized relay C1 at field station, wire 88 to negative terminal of line battery. The stick circuit for relay C is over its contact f93 and b65 of relay LCS. The stick circuit for relay CS is over f94 of relay L and f95 of relay CS. The relays CH are governed by polarized circuits so as to be dropped whenever the associated switch 4 SML or 2-3 SGL is moved to a new position, the new circuit for the relay being through its stick contact so as to cause a reverse flux that drops the relay away for initiation of a control cycle. Assuming lever 4SML is moved to its right-hand or reverse position relay 4CH drops away opening its stick contact f60 and at its contact b68 relay 4LC is picked up over b66 of relay LCS. On picking up relay 4LC is held over its upper winding by a circuit in series with relay LCS over b69 of relay CPP, b70, b71, f72, f73, winding of relay LCS, and f74. Relay LCS on picking up opens at b75 the energizing circuit of the magnetizing stops of the oscillator CT. The oscillator is released and commences to oscillate. On picking up relay 4LC at f78 pickups relay 4CH over f79 of relay LCS. Similarly in the case of actuation of lever 2-3SGL relay 2-3CH is pole changed and drops away effecting the pickup of relay 2-3LC and relay LCS. This relay LCS is held throughout the control cycle along with the associated relay LC by circuits over f82 of relay LCS and multiple connected contacts f83, f84, f85 and f86 of the bank relays. Relay LCS, at b65, opens the normal stick circuit for relay C and relay C opens the line circuit at f90 so that relays L and L i drop away. At f94 of relay L the normal stick circuit of relay CS is opened and relay CS drops away to open f91 in the line circuit and at b96 picks up relay CSP which remains picked-up until relay CS is again energized. At the field station relay L1 on dropping away at f97 at the beginning of a cycle causes release of start cycle relay CS1. Stepping operation. Assuming initiation is made for the transmission of a reverse points control code for the points 4W, Fig. 1B, the oscillator CT, Fig. 1A, having released, on rotating through its neutral centre position, opens the contacts 41, 45, Fig. 1A, and opens the normal stick circuit of relay 1V extending over contacts 41, 45 and f98 of the relay. Relay 2V whose stick circuit is over f100 of relay 1V, f101 of relay 2V and f99 of relay 3V is maintained energized by an alternative circuit over contacts 44, 48 of the oscillato