| 摘要 |
PROBLEM TO BE SOLVED: To accurately diagnose troubles of a game ball detector. SOLUTION: In the diagnosing of the game ball detector 4 having a light emitting part 1 and a photodetecting part 2 for receiving light from the light emitting part 1, a value of a constant current for driving the light emitting part 1 is increased gradually per specified time under the condition of detecting none of game balls 3. When the output potential of the photodetecting part 2 indicates the state of detecting any game ball, the game ball detector 4 is determined to have a trouble and an abnormality flag is set.
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