| 摘要 |
PURPOSE:To change a connection for each card without stopping the actuation of an entire power supply device by providing a changeover switch to a power supply line of a digital input circuit. CONSTITUTION:When a relay contact, a switch, etc., for example, is closed as a no-voltage contact 21 that opens and closes in response to the state of a plant, the current of a power supply device 22 for input circuit is limited by a limiting resistance 25 and flowed to a photocoupler 24. Then the current is transmitted to a logical circuit from the coupler 24 by the light emission to detect that a no- voltage contact of a logical circuit 27 is closed. Under such conditions, a power supply switch 26 set into a card 20 can be opened regardless of the state of the contact 21. Thus it is possible to stop the current flowing to the coupler 24. Therefore, the connection of a connector 23 can be changed without stopping the actuation of the device 22. |
