| 摘要 |
PURPOSE:To make unnecessary a signal input for grasping the state of an external device and to sharply reduce the cost of apparatuses and cable work by adding a current deciding circuit to a digital output substrate. CONSTITUTION:Current flowing to excite a relay 4 in the external device 3 on the basis of an output signal 2 from the digital output substrate 1 is always monitored by the current deciding circuit 5, and when the current value exceeds a certain threshold, the circuit 5 decides that the operation of the relay 4 is executed and outputs the decided result as a state signal 6. The state of the external device 3 can be grasped by using the state signal 6 without independently inputting a response signal from the external device 3. Since it is unnecessary to independently inputting the response signal to an output signal from a programmable controller or the like, the preparation of the state signal, the preparation of the input substrate and cable work between the substrate 1 and the external device 3 can be omitted and the price can be sharply reduced.
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