GB797140A - Improvements in code communication systems - Google Patents

Abstract

797,140. Patternmovement stepping registers. GENERAL RAILWAY SIGNAL CO. Aug. 16, 1955 [Aug. 17, 1954], No. 23615/55. Class 106 (1). [Also in Group XXXVIII] In an electronic pulse code communication system, e.g. for the control of track switches, signal devices &c. at one or more remote field stations along a section of railway from a control office, and the transmission of indications to the control office (see Group XXXVIII), each field station is provided with a shift register 19 which prior to the reception of a control code is selectively conditioned in accordance with an indication code to be transmitted to the control office, and when the received control code is stepped into the first stage of the shift register the stored indication code is stepped out of the last stage. Each stage of the shift register comprises two grid-controlled cold cathode tubes, a storage tube 360 providing for the storage of a code digit, and an intermediate tube 361 providing a temporary storage for a digit as it is transferred from one stage to the next. The cathode of each storage tube is connected to wire 115 and the cathode of each intermediate tube to wire 116, the wires 115 and 116 being supplied with square-wave shift pulses of opposite phase. Each storage tube, other than that in stage 0, receives an input from the plate of the intermediate tube in the preceding stage and each intermediate tube receives an input from the storage tube in the same stage. Prior to the reception of a control code, positive-going code impulses indicating the condition of controlled apparatus are applied in parallel mode to the grids of the storage tubes of the appropriate stages Nos. 1 to 15 to. cause these tubes to fire. The shift pulses on wires 115 and 116 then step the indication code from stage to stage, the final stage No. 15 having its tubes made selectively non-conductive and conductive on successive pulse periods in a time-spaced pattern and an output being taken from this stage to modulate a carrier transmitter to transmit the indication code to the control office. As the indication code is stepped out of the shift register a control code in serial mode is applied over wire 397 to the grid of tube 360 in stage No. 0 of the shift register and is transferred from stage to stage by the shift pulses until the storage tubes of stages Nos. 1 to 15 are conductive or non-conductive in a pattern representing the control code. The occurrence of the shift pulses is synchronized with the received control code digits in such a way that wire 115 is always at a low potential as each code digit is applied to the grid of tube 360. The control code stored in the register is then utilized to selectively operate relays 20A or 20B in response to the operation of relay 121 or 131 by a further timing pulse. To cancel all signals stored in the shift register in readiness for the next cycle of operations the voltages on wires 115 and 116 are caused to be in phase.