| 摘要 |
PURPOSE:To prevent the wrong coupled control despite occurrence of a wrong signal by using an input lock circuit which performs control to validate or invalidate the input data received from a facilities equipment or a process input/output devices with a command given from a central processing unit. CONSTITUTION:A control signal is sent to a process input/output device 20 from a central processing unit 1 to turn on a relay RL1 of an input lock circuit 23. Thus the digital signal received from a facilities equipment 4 is validated. While this digital signal is invalidated when the relay RL1 is turned off. If it is supposed that a wrong signal is produced owing to a maintenance state of a facilities equipment 4A, etc., this fact is given to the unit 1 with a direct command. Then the unit 1 gives a command an input lock circuit 23A to lock the input signal and therefore the signal sent to the device 1 from the equipment 4A is locked. As a result, a wrong signal is never sent to the unit 1 even though the wrong signal is produced at the equipment 4A with maintenance after a circuit 23A is locked. Then a facilities equipment 4B set at the other side never receives the wrong coupled control.
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