Patent GB-883105-A (GB)
Title: Improvements in or relating to signalling arrangements for remote control systems
Inventor: NICHOLS JOHN WINFRITH DE LISLE
IPC: H04Q9/14
Filed: 1959-09-01
Abstract: 883,105. Electric selective signalling systems. CORPORATION OF THE TRINITY HOUSE OF DEPTFORD STROND., and A. T. & E. (BRIDGNORTH) Ltd. Aug. 9, 1960 [Sept. 1, 1959], No.29724/59. Class 40 (1). (BRIDGNORTH) Ltd. Aug. 9, In an electrical signalling system for the transmission of information between a control station and any one of a plurality of remote stations over a single channel, the information transmitted from a remote station comprising the address of the remote station and the condition of each of a plurality of equipments at that station, the control station comprises means for receiving the information transmitted by a remote station, a storage device individual to each remote station for storing information relating to the conditions of equipments last received from the remote stations, means for automatically selecting in accordance with a received address the appropriate one of said storage devices and for displaying the information contained therein, and means for simultaneously displaying the new information accompanying said received address so that the two displays may be compared. As described the central station can select any one of sixteen field stations, by transmitting a signal of the kind illustrated at (a) in Fig. 1, using two different frequencies f 1  andf 2 , and can effect up to sixteen controls at the selected field station by means of " function code " pulses. Each field station transmits to the central station the states of twenty-five switches at the field station whenever any one changes its state, this being effected by the signal shown at (b) in Fig. 1 using two frequencies f 3  and f 4 . The central station on receipt of a warning pulse from a field station applies the frequency f 2  to the line which pre. vents any other field station initiating a transmission. At the central station, Fig. 2, address keys AK and control keys CK are set to select a desired field station and a desired control and this causes a circuit CCC to route pulses from a generator IG1 to leads LF1 and LF2 which, in turn, causes the desired sequence of frequencies from oscillators FG1 and FG2 to be applied to a transmission line TL. These signals are received by tuned filters F1,F2 at each field station and at the selected field station a selection relay SR responds to permit the subsequent control pulses to pass to a control recoding circuit CR which effects one of the sixteen controls. When any one of twenty-five switches at the field station changes its state the field station transmits indications of the states of all of the switches to the central station by means of an impulse generator IG2 and oscillators FG3 and FG4. These signals are received by tuned filters F3 and F4 at the central station and the address signals are recoded by a device CDC to select one of sixteen storage units. The next twenty-five signals are then registered in an intermediate register IR common to all the storage units and at the end of the transmission they are transferred to the storage unit previously selected by the address signals. Each storage unit comprises two registers DR and SS. The signals representing the states of the twenty-five switches go first to register DR where they can be compared visually with the previous states of the switches registered in register SS and then in response to a control signal TC they are transferred to the register SS. A comparator device DDC may be provided to indicate which switches have actually changed their states.