GB1280742A - Remote control system - Google Patents

Abstract

1280742 Controlling remote stations from a central station INTERNATIONAL STANDARD ELECTRIC CORP 24 March 1970 [4 April 1969] 14113/70 Heading G4H A remote control system includes a central station PC and one or more remote stations PS1, the central station transmitting a control message containing the address of an apparatus unit in a remote station and successive messages transmitted to the same controlled remote station being time spaced so that the remote station has sufficient time to carry out each order in successive messages. The central station is connected by transmission lines lg to each remote station and contains a memory MM read by a program unit BP, a control panel TAB scanned by a scanner EX and transmitters EM0-EM2 connected by a multiplex channel CM to the unit BP. Each remote station includes a receiver RX, a logic circuit LC controlled by a redundancy check circuit OPR and a connector CO adapted to actuate a relay on receipt at the remote station of a control message. To carry out a remote control operation, a control button bt corresponding to the apparatus unit, i.e. a relay in the remote station is depressed and the unit BP receives a signal from the scanner. The unit BP sends to the memory MM a request to send a message, this information being stored in the memory. The unit BP reads the memory which contains orders each accompanied by a time denoting the time after which the orders may be sent, successive orders for the same remote station being appropriately time spaced. The transmitters are scanned by the program unit BP which, on finding an idle transmitter, reads the earliest control order in the memory and its associated time indication. This time indication is compared with the actual time supplied by a clock HG. If the actual time is later than the time indication of the control order, a control message is transmitted to the remote station. The message contains the duplicated address of the apparatus unit to be controlled, the address of the remote station and a redundancy character. The message causes closure of the relay for a pre-set time. The logic circuit LC checks that the duplicated addresses are in fact identical by means of a comparator and also checks that the remote station address is correct. The circuit OPR performs a redundancy check on the message and if message errors are detected by the logic circuit or the circuit OPR an audible or visible fault indication is provided whereupon the remote station is reset to accept the next message. A cyclic check is repeatedly applied to each remote station by repeatedly sending a checking message to each remote station.