Patent GB-892420-A (GB)
Title: Improvements relating to remote control systems
Inventor: COLEY JAMES PERRIN
IPC: H04Q9/04
Filed: 1957-05-23
Abstract: 892,420. Electric selective-signalling systems. WESTINGHOUSE BRAKE & SIGNAL CO. Ltd. May 23, 1958 [May 23, 1957; Dec 4, 1957], Nos. 16357/57 and 37760/57. Addition to 886,663. Class 40 (1). [Also in Group XIX] In a remote control system, suitable for use in railway signalling systems, as claimed in the parent Specification, the controlled apparatus is divided functionally into a number of groups each provided with separate scanning means which in response to stepping signals are rendered operable in turn to provide scanning of said groups of apparatus in step with the scanning in sequence of the position of the control devices at the control office which correspond to the apparatus in each group. First embodiment: As shown, Fig. 1, a field station F1 comprises a counting chain C1, the last stage of which when actuated causes the closure of a circuit for stepping pulses from the control office (not shown) to the next field station F2. The station F1 includes amplifiers A1, A2 for the two directions of transmission and hybrid transformers H1, H2 which, together with balancing networks B1, B2 isolate the transformer outputs from each other. The amplifier A2 is continuously active to transmit the incoming indication codes but the amplifier A1 normally prevents transmission of the control and stepping signals from the control office to the next field station, and becomes active in response to a signal caused by the change of state of a transistor of a bistable circuit in the final counting chain stage. Second embodiment (Fig. 2, not shown): a band-stop filter tuned to reject the stepping frequency and to pass the control and indication frequencies is in parallel with a band-pass filter tuned to pass the stepping frequency but not the control and indication frequencies. Third embodiment (Fig. 3, not shown): the stepping pulses are applied to all the field stations, but the counting chains do not respond until primed, the actuation of the final counting chain stage of each station causing a priming signal in the form of a steady D.C. signal to be applied to the next station to prime the counting chain at the next station, the transmission lines at each stage being blocked for D.C. by capacitors. In a fourth embodiment (Fig. 4, not shown), priming signals in the form of a distinctive carrier frequency are employed. In a fifth embodiment, Fig. 5, each field station such as F1 has a distinctive stepping frequency and at each station there is a band-pass filter U1 tuned to pass the associated frequency to the counting chain C1 at the station. The Control Office for the fifth embodiment, Fig. 6, comprises transmitter selector circuits such as SF1, SF2, each comprising bistable transistor circuits having inputs supplied over condensers C1, C2, the first stage of the chain CP1 being connected to the condenser C1 and the first stage of the chain CF2 being connected to the condenser C2. Circuits comprising transistors TR5, TR6, supply the transmitters over lines LT. On operation of the first stage of the chain CF1, the transistor TR1 is rendered conducting and the transistor TR2 non- conducting to remove bias from the transistor TR6. The output waveform of a stepping generator MSG for the stepping pulses which generator is in the form of a transistor multivibrator circuit is therefore effective to cause the transistor TR5 to produce a waveform on the line LT for transmission of the stepping pulses by a distinctive carrier link to the corresponding field station. When the scanning cycle reaches the first stage of the chain CF2, the selector circuit SF1 is rendered ineffective and the next circuit SF2 is rendered effective to cause the stepping pulses to be transmitted over the second distinctive carrier link. Sixth embodiment (Figs. 7, 8, not shown): a binary counter (see Group XIX), comprising a plurality of cascade-connected bistable transistor stages is provided at each field station, except the first. When the counter registers the number of step periods in the scanning cycle of the prior field station, an " and " gate is actuated and an output obtained to prime the counting chain of the associated field station. The output may alternatively be obtained from the final counting stage of the binary counter, if a predetermined count is imposed on the counter each time it is reset.