| 摘要 |
This onboard device measures the received power of radio waves transmitted from a base station while the engine is running and sets a near-out-of-range flag when the level of the received power has become equal to or lower than a near-out-of-range level, which indicates the possibility of going out of range. The onboard device permits a portable terminal device to obtain a new effective period for a key ID when the radio wave environment of a vehicle when the engine is stopped indicates that the vehicle is out of range, and the effective period of the key ID has expired and needs to be renewed, provided that the near-out-of-range flag has been set. Consequently, security can be enhanced during acquisition of update information for the key information with the portable terminal device. |
