Patent GB-1033105-A (GB)
Title: Improvements in or relating to protection arrangements for railway systems
IPC: B61L25/02
Filed: 1963-03-29
Abstract: 1,033,105. Automatic train control. SIEMENS & HALSKE A.G. March 29, 1963 [March 30, 1962], No. 12641/63. Heading B7N. In a system for indicating the position of a train in a line region, e.g. region b, Fig. 1, controlled from a central office B and for automatically controlling the progress of the train in accordance with the ahead traffic and the state of the track, the track region is divided into a number of equal sections b1-b20, defined by the cross-overs in a trackside loop Lb connected to the central office and coupled by pick-up coils to apparatus on the train The office supplies a continuous signal of frequency f1 to the loop and the vehicle apparatus by detecting and counting the number of crossover points passed can determine at any instant the section it occupies and in response to an interrogation signal passes this information by means of an acknowledgement signal to the office. The office equipment for line region b, Fig. 2, comprises a decoupling unit 21 which passes the acknowledgement signal at frequency f3 via receiver 22 and decoding unit 23 to an occupancy store 24, which includes the same number of storage positions as there are sections to the line region and the relevant positions is switched to its occupied state. Each position of the store, starting at position 1b20 is interrogated in turn by a counter 25 which is stepped forward by pulses produced in pulse timer 26. If a store position is in an unoccupied state the timer steps the counter on to the next position, but if an occupied position is detected a time switch 27 is switched to its operative state in which it renders timer 26 inoperative for a set time and a frequency modulated interrogation signal for the train is generated in coder 28 and transmitter 29, e.g. by keying the signal at frequency f1 to frequency f2. The signal comprises two parts, a first part which denotes the consecutive number of the line section with which the occupied position of the store is associated, hence the apparatus of the train in that section is able to determine that the signal is addressed  thereto and in response returns an acknowledgement signal which indicates the section occupied. The second part of the signal is controlled by the count in a second counter 30 also supplied from the timer 26 which is reset each time an occupied position in store 24 is interrogated and hence indicates before being reset the number of clear sections ahead of the occupied section being interrogated. This number is modified by the number of sections which are occupied by the train in advance and also by information relating to the state of the track &c. stored in unit 32 which is also interrogated by counter 25. The train apparatus includes pick-up coils 54, 55 coupled via decoupling units 56, 57 to receivers 58, 59 responsive to frequencies f1 f2 respectively. The output of receiver 59 is applied to decoder 60 which supplies the first part of the interrogation signal to a comparator 53 in which it is compared with an acknowledgement signal selected by coder 52, representing the number of sections counted by the vehicle and stored in unit 51. If coincidence is detected the coder 52 initiates the transmission of the acknowledgement signal via transmitter 62, phase shifters 63, 64 and decoupling units 56, 57. Furthermore, an inhibiting circuit 65 is opened by comparator 53 and the information in the second part of the signal, for the control of the train, is transmitted from decoder 60 to an indicating and train control arrangement 66. On passage over a cross-over an output pulse is generated in discriminator 65 which is applied to an intermediate store 67 where it remains until the next interrogation signal from the central office. Comparator 53 detects coincidence between this signal and the selected acknowledgement signal then passes the stored pulse to counter 51 and causes transmission of a modified acknowledgement signal indicating that the train has entered the next section. This positional signal is stored in the central office and the previous signal is erased. Means are also provided for indicating to the train when it is about to enter a line region, for resetting counter 51; for informating the next line region that a train is about to enter and for informing a preceding line region office of the number of clear sections between the entry to the region and the last train to enter.