Patent GB-489206-A (GB)
Title: Improvements in or relating to electric control and/or indicating systems
IPC: B61L7/08
Filed: 1937-07-30
Abstract: 489,206. Electric control and signalling systems. GENERAL RAILWAY SIGNAL CO. July 30, 1937, No. 21204. Convention date, Aug. 1, 1936. [Class 40 (i)] In a system of remote control and indication more particularly for controlling and supervising railway traffic control of apparatus at outlying stations is effected by coded combinations of impulses of simple or complex frequencies and indication at the control office is effected by a code series of impulses of the same frequency but different from the frequencies employed for the control code the code being characterized by the spacing of the impulses. Transmission and reception are effected by synchronously operated relay chains and the nature of the codes used facilitates duplex working. Figs. 1A-1D show the equipment in the control office and Figs. 2A, 2B that at one of the field stations. As shown the system is applied to the operation and supervision of the points and signals of a railway track. If desired communication may be effected over an existing telegraph or power line. General operation. The central office and the field stations are provided with chains of relays which are operated step-by-step in synchronism during the progress of a communication. In the event of a change in the condition of apparatus at a field station, a, cycle of stepping operations is initiated by an impulse of frequency f<0> followed by an impulse of frequency f<4> for condi- .tioning the various circuits after which further impulses f<4> characteristically spaced are transmitted to indicate the condition of the station apparatus. If initiation of the cycle takes place at the control office as the result of the operation of a control key, an impulse of frequency f<1> is applied to the line for conditioning purposes and during stepping, impulses characteristic of the control to be effected are transmitted, each impulse being of frequency f<1> and/or f<2>. initiation of operation and conditioning apparatus for receiving control codes. Depression of the " start " button ISB, Fig. 1A, pulls up relays SR, CD, LS the latter preventing operation of the CD relays corresponding to other stations and pulling up relay C which starts up the frequency generators F<1>, F<2>, F<3> the generator F<3> applying its frequency f<3> direct to the line 112, 113. Relay C pulls up relay IF which applies frequency f<1> to line. Relay IF operates F, SA, SB, VP, the latter of which pulls up E and releases IF to remove f<1> from the line and terminate the conditioning period. During this period, relays IF<1>, Fig. 2A at all the substations are operated over the f<1> channel A<1>, ILC<1> IA<1> and relays SO<1>, SOS<1> at the stations are locked up. At the termination of this conditioning period, relays SOS<1> fall back but relays SOl remain locked up. Stepping and code impulsing. When IF releases, FB releases and pulls up the first counting relay IV of the office chain IV, 2V, 3V which releases E and again pulls up IF and /or 2F over a circuit including station selecting switch 9. As shown, the switch 9 is positioned so that the first code impulse of frequency f<1> is transmitted and at the field station shown it maintains relay SO<1> operated owing to the position of jumper 199. A code impulse of another or other frequencies would allow the release of SO<1> and the dropping out of the station. At the end of the first code pulse VP is released and E again pulls up to release IF. This brings about operation of the 2nd chain relay 2V, the release of E and operation of the relays 1F, 2F in accordance with the position of signal control relay SGL. In the position shown, both relays IF, 2F are .operated and a second code pulse of frequency f<1>, f<2> is transmitted to the field station where relays IF<1>, 2F<1> are picked up and a circuit is closed over contact of chain relay 2V<1> for relay SS<1> which operates the track signals to a " stop " position. If the 2nd code impulse is of frequency f<1>, relays SS<1>, SGR<1> are operated and " clearing " signal relay ES<1> is pulled up. Similarly a pulse of frequency f<2> operates clearing signal WS<1>. A 3rd pulse of characteristic frequency is then sent for making a further selection (not shown), and chain relay 3V is pulled up as the result of further operation of relays F, FA, FB, E. At the end of the 3rd pulse relays 1F or 2F, F remain, down for a sufficiently long time period to allow SA to drop, and release C which releases the stepping chain and also SC which facilitates restarting either by a field station or by another CD relay. The release of C also stops the operation of the frequency generators F<1>, F<2>, F<3>. Release of the station relays SA<1>, SB<1> allows the selected field station relay SO<1> to fall back. Conditioning for transmission of indication. A change in the condition of apparatus at a field station results in the release of CH<1>, Fig. 2B. Release of CH<1> pulls up SI<1> which remains up during the indication code, and starts the operation of the oscillation pentagrid mixer OSM<1>. The mixer OSM<1> generates a, frequency f<0> which is subsequently modulated by the frequency f<1> (grid 194) which is applied to the line wires at the control office in response to the receipt of f<0> and is received over 3LC<1>, 3A<1>. The plate current frequencies therefore are combinations of the oscillator frequency f<0> and the frequency f<3> and result in the production of a frequency f<4>. Transmission of f<0> pulls up relay MB, Fig. 1C which picks up CF to start the frequency generators in the control office. CF also picks up 2F which applies f<2> to line during the impulse periods of the stepping cycle. As soon as f<3> is applied to the line it beats with the oscillator frequency f<0> and the resultant frequency f<4> is used for transmitting indications. During the " conditioning " period previously described in connection with the control office operations, SB<1> is operated and f<4> is removed from the line and during the following " pause '' relay MB is released by relays FB, E. Registration of field station. The code for transmitting from a field station, the indications corresponding to the alternative positions of the various apparatus comprises impulses of frequency f<4> each of which may be prepared for application to the line during either the " pause " or " impulse " periods of the stepping cycle and transmitted and rendered effective at the central office during the next two successive periods. The code impulses characterizing the field station is determined by the jumpers 188, 189. During the conditioning period, i.e. when FB<1> is up, PB<1> pulls up over jumper 188 and prepares for the transmission of the 1st indication pulse f<4> during the 1st pause, i.e. when FB<1> is again released. This frequency is received at the control office by the circuit 4LC, 4A1, 4A2. If the jumper 188 is in any other position, PB<1> is not picked up and no code impulse is transmitted. The 1st indication pulse is terminated when FB<1> picks up during the first stepping impulse and a second pulse indicating a further condition may be transmitted or not during this period as determined by the jumper 189. At the control office, MB is pulled up by the 1st pulse which is effective to pull up 1PT over contacts of MB, IV at the beginning of the first stepping impulse. The second indicating pulse received also during the first stepping pulse pulls up MF which at the beginning of the second " pause " pulls up 2PT. The relays 1PT, 2PT are characteristic of the field station shown and pull up the appropriate station relay ST. Transmission of indications. Similar operations occur in transmitting the code impulses representative of the condition of the track relay T<1> and the " all clear " relay M<1> during the pauses and steps associated with the second and third stepping impulses, to effect the corresponding conditioning of the indicating relays 11R, 21R. Lock-out between stations. If changes occur simultaneously at several field stations, the SI<1> relays at those stations are pulled up. The arrangement however is such that irrespective of the number of stations ready to send in indications, such stations are dropped out by the release of the SI<1> relays one or more at a time during each step of the cycle of operations until only one station, i.e. the one having a superior code is left with its SI relay energized. The arrangement whereby the local frequencies f<0> are combined with the frequency f<3> transmitted from the control station to produce station frequencies f<4>, ensures similar phase relations of the frequencies f<4> at all the stations. Duplex operation. The nature of the codes employed allows distinctive signalling in both directions simultaneously.