Patent attributes
A vehicle theft deterrent system includes a smart card key system. The theft deterrent system is adapted to output a warning sound from a buzzer upon detection of a vibration of a predetermined value or larger by a vibration sensor. The buzzer prevented from operating at a time of unlocking a seat or unlocking a fuel lid. When an on-board device detects that a seat unlocking switch, for example, has been operated and upon success of mutual authentication after communication with a portable electronic key, the on-board device switches the state of operation of a buzzer into a non-operable state. Therefore, when a user who carries a regular portable electronic key does not want operation of the buzzer, the buzzer can be positively switched to the non-operable state.
