| 摘要 |
PURPOSE:To detect states of contacts with the small number of wiring by connecting electronic switches to the contacts, connecting terminals on the opposite sides from the switches to a receiving circuit in common by wiring, and inputting the on-off signals of the switches to the receiving circuit. CONSTITUTION:Electronic switches 2 connected to contacts 1 are turned on in order by a ring counter 3. Then, 5 or 0V is inputted to a gate circuit 5 according to a contact 1 connected to a switch 2 is made or broken. A counter 3 which supplies inputs to the switches 2 and a counter 3 which supplies inputs to selectors 6 have the same constitution and a preset signal 8 and a clock signal 9 are made common, so that the contacts 1 correspond to D type FFs 7. For the purpose, a signal transmitted to the receiving circuit in synchronism with the on-off operations of switches is inputted to detect the on-off states of the contacts with the small wiring.
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