| 摘要 |
A counter increases a counted value at regular time intervals during a transmission time of a request signal Sr transmitted based on trigger signals input from a door unlocking sensor or the like. On the other hand, the counter decreases the counted value at regular time intervals during a non-transmission time of the request signal Sr. A determination unit either prohibits or permits transmission of the request signal Sr to a portable unit, based on comparison results of the counted value with a prohibition value and a lifting value.
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