| 摘要 |
When a predetermined condition is met while the engine is running (S 1 ->yes), the output of an alternator is reduced (S 2 ). Then, a request signal which requires a response from a portable unit is delivered in the vehicle and an ID signal output from the portable unit in response to the request signal is received. Based on the received signal, a judgment is made whether or not the particular portable unit is present in the vehicle (S 3 ). If it is judged that the portable unit is not present in the vehicle (S 4 ->no), an alarm is given (S 5 ). By so doing, the influence of electromagnetic noise caused by surge noise of the alternator is avoided to allow detection of the portable unit in the vehicle with accuracy, thereby reducing the possibility of causing an erroneous alarm.
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