| 摘要 |
PURPOSE:To secure the safety of a control system by detecting the operation state of an output device in the final stage and operating exclusive OR between this state and the output signal of a CPU unit to detect the trouble of an output unit by the CPU unit. CONSTITUTION:When continuity trouble or contact welding trouble of an electromagnetic relay 9 occurs in a transistor of an electromagnetic relay driving circuit 8 when a CPU unit 1 does not output the output, the voltage from a power source 10 for external driving device is not applied to a voltage converting circuit 12. Consequently, an exclusive OR element 12 outputs the low level, and an inverter element 14 inverts it to output the high level. This output in the high level is delayed in a time delay circuit 15 by a prescribed time and is inputted to the unit 1 by an input port 18 to detect the trouble. The circuit 15 is provided to absorb the time difference between an output port 7 and the voltage converting circuit 12, and an LED indicator 16 is lit when the output is in the high level. |
