Patent GB-826520-A (GB)
Title: Improvements in or relating to railway centralised traffic control systems employing axle counters
IPC: B61L1/16
Filed: 1957-05-23
Abstract: 826,520. Railway centralized traffic control systems. SIEMENS & HALSKE A.G. May 23, 1957 [May 25, 1956], No. 16435/57. Class 105. In a railway C.T.C. system wherein the free or occupied condition of a track section is indicated by counting electrical impulses representing the incoming and outgoing axles apparatus is provided at the central control office for selectively receiving and counting the impulses appertaining to respective sections generated in response to axles entering and leaving the sections. The impulses appertaining to an axle entering or leaving a section are modified by a characteristic feature identifying the impulse according to entry or exit and according to the section, all impulses being transmitted to the central control office over the same transmission channel which may be one used for purposes other than axle counting. Such impulse characteristic features are different types of current, impulse shapes, impulse frequencies, carrier frequencies, frequency or impulse modulation. At the central office the receiving counters have appropriate selection means appertaining to the respective counting points. In the embodiment shown, a single-track has three passing loops with five counting points A, B, C, D and E each provided with mediumfrequency generators G1-G10 for generating impulses of carrier frequency, which is modified to identify the impulses respectively generated by an axle entering and leaving a section, and the frequencies of the pair of impulses appertaining to a section being different from the frequencies of the pairs of impulses of all other sections. All these impulses are transmitted through the same line L to the central office Z at which by means of appropriate frequency filters F101-F112 the impulses are selected and directed to the appropriate counters AZA, AZB, AZC, AZD or AZE each appertaining to the respective counting points A-E. The equipment at points A and B operates in like manner, the output from the pulse generators G1, G4 being fed continuously in closed supervisory circuits through filters F1, F4 to appropriate selecting devices F101, F104 at the central office Z to supervisory indicators RUA and RUB respectively. These supervisory circuits are interrupted during the impulse periods of the generators G2, G3, G5, G6, the impulses being selected at the control office by filters F102, F103, F105, F106 respectively and fed to the appropriate impulse counters AZA, AZB, the outputs of which operate a track indicator FM-AB to indicate whether or not the section AB is occupied. In the case of counting point C one impulse circuit including the generator G7 is assumed to be a normally open circuit and the impulse circuit including the generator G8 to be normally closed. At the control office Z the impulses of frequency G7 and G8 are selected respectively by filters F107 and F108 and fed to the counter AZC. The outputs of counters AZB and AZC operate a track indicator FM-BC1 for the track section BC1 or indicator FM-BC2 for the passing siding BC2. In the case of points A, B or C local sources feed the generators G1-G8. At points D and E the power for the generators G9, G10 and Ge is obtained through the line L from a generator G20 at the central office through filter F120 and is received at the points D, E through filters F20d and F20e respectively and rectified in rectifiers GRd and GRe. At point E the two impulse frequencies are produced in modulators M11, M12 as the sum and difference frequencies of the frequencies of generators Ge and G20. At points D and E one open impulse circuit and one closed impulse circuit are provided.