Patent GB-906599-A (GB)
Title: Improvements to remote control and signalling systems
IPC: H04Q9/14
Filed: 1959-04-24
Abstract: 906,599. Electric selective signalling. STANDARD TELEPHONES & CABLES Ltd. April 24, 1959 [April 24, 1958], No. 14147/59. Class 40 (1). A signalling and control system comprises a main station and one or more field stations at each of which there are a number of devices, e.g. switches, to be controlled from the main station and the position of which is to be indicated at the main station. Control switches at the main station, one for each device to be controlled, are connected to an address register, the cells of which are scanned in turn in repeating cycles. The conditions of the switches in each cycle are stored for comparison in the next cycle with the conditions in that cycle. A difference between present and previous cycles causes the scanning to stop and a call signal is transmitted including the address of the device which is to be changed. The appropriate field station responds by signalling back the same signal which is checked at the main station against stored data. The main station then issues a control signal (the same signal, as for the call) now operative to change the state of the selected device. In the opposite direction, if the state of any device changes at a field station a similar scanning arrangement discovers the change by comparison with stored data from the previous cycle. Scanning then stops and a call signal identifying the device is sent to the main station, which selects the appropriate indicator circuit and transmits a " ready " signal. The field station then transmits the change signal and the appropriate indicator at the main station is reset accordingly. Main station.-A circuit individual to a particular device at one of the field stations is shown at OR1, Fig. 1. The control switch has two " turn " positions TA, TB for putting the device into either of its two positions A or B. A push-button P1 initiates the control, one of a pair of core storage units MA, MB, is set according to whether the control is in position TA or TB, and a trigger AB controls an indicator lamp L showing that the state of the corresponding device is to be changed. These individual circuits are scanned in turn by an address distributer circuit DA, which causes the setting of units MA, MB to be compared with their setting in the previous scanning cycle now stored on a trigger in circuit CL. When a difference is found it is necessary to initiate a " control message " to change the state of the corresponding device at a field station. When a difference is found the corresponding address passes to an output store in circuit CL and also to a transfer storage circuit MT. The operation of circuit CL is controlled in a sequence of steps by a ring counter DT having nine stages, the last stage of which steps the address distributer circuit DA. This circuit delivers successive addresses as combinational signals on parallel leads. These signals pass to the recoding matrix MDA, the output from which gives a coded representation of each address in turn, in which form the addresses are recorded in circuits CL and MT when a control switch is found changed. The address signals recorded in the output store of circuit CL and those recorded in circuit MT are compared by a circuit CC. When there is proper agreement the control signal is recorded in the output store in circuit CL and the counter DM is started by pulses from timebase BTE. Time-bases BTE and BTR alternatively provide timing pulses for the control of transmission or reception of signals. Pulses pass to a counter DM, the parallel output of which is converted in a matrix MDM to give successive timing pulses on leads M0-M11 in turn. The last stage of counter DM steps a four-position counter P which determines the order of tranmission operations: C1, first sending of Main station; C2, first sending of field station sending; C3, second sending of main station; C4, second sending of field station. These outputs gate the timing pulses from sources BTE or BTR alternatively to the counter DM. The parallel leads from circuits CL and MT are selectively energized in accordance with the message which is to be sent and, under the control of the pulses from leads M0-M11, these digits are serialised in circuit TP-S and applied to line via an And gate enabled by " sending " signals on leads C1 or C3. The first digit is a " start " signal and this is followed by digits indicating whether the message is for control purposes, or asking for an indication. This is followed by the address of the device to be controlled, read out of store MT and the position to which the device is to be moved (A or B). The last impulse stops the counting circuit DM. This transmission occupies C1 time of the counter P. The field station receives the " start. " signal and its counter starts under control of a time-base so that the successive digits can be properly interpreted. The incoming message is stored in a series of triggers similar to those of store MT and retransmitted to the main station for checking purposes. Checking.-At the main station the returning message is passed through an And gate opened by the reception signal in C2 time. Simultaneously, the message is read out of the transfer store MT and compared digit-by-digit with the incoming message, by circuit CCT which prevents further operation if a disagreement is detected. In the third phase C3 the message is transmitted again to the field station and a similar check is made, the selected device being reset (A or B) by energization of a corresponding relay. In the fourth phase C4 an indication is transmitted from the field station that the device is now in its changed position. The rest of the message is skipped. The circuitry at the field station is similar and a message may be initiated when a device changes its state, to cause an indication of this to be made at the main station. This transmission also consists of four phases with checking at each phase. Provision is made for detecting the occurrence of faults in the individual circuits. A delay device delays action on the occurrence of a fault to prevent signalling a transient fault. If a fault still remains after the delay period an alarm is given. A fault appearing in the decoding matrix MDA is also detected and a different alarm is given. Tests to ensure that the system is working properly are described. Transistors may be used in the electronic devices of the system.