| 摘要 |
PROBLEM TO BE SOLVED: To provide a key input device capable of immediately detecting the occurrence of a key fault and also normally reading a key operation in the case the fault occurs. SOLUTION: This device is provided with a transfer switch 1 in which connection contacts are switched over by operating a key, diodes 2a and 2b are connected to the break contact 1a and the make contact 1b of the switch respectively so as to make their current directions reverse to each other, and the contact state of the switch 1 is detected on the basis of the conductive state of the switch 1 by alternately feeding power between the diodes 2a, 2b and the fixed contact 1c of the switch 1 in a reverse direction.
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