Patent ID: 8031048

Claim:
A vehicle antitheft system in which verification of encryption codes is made between a mobile unit that a driver carries and an on-vehicle unit that is mounted on a vehicle, and when the encryption codes for verification are coincident, said on-vehicle unit permits the vehicle to move, the vehicle antitheft system comprising: mobile unit verification encryption code transmission means for causing a mobile unit verification encryption code having preliminarily been stored in a storage part of said on-vehicle unit to be transmitted to said mobile unit by operation of said driver; determination means of said mobile unit for determining whether or not said mobile unit verification encryption code having been received is the one that is transmitted from his own vehicle; reply means of said mobile unit for replying a response signal corresponding to said mobile unit verification encryption code to said on-vehicle unit when the mobile unit verification encryption code that said determination means has received is determined to be transmitted from his own vehicle; and on-vehicle unit control means for outputting a control signal permitting the vehicle to move in the case where said response signal having been replied corresponds to said mobile unit verification encryption code; wherein during traveling of the vehicle, said on-vehicle unit control means transmits at regular intervals said mobile unit verification encryption code that is stored in the storage part of said on-vehicle unit to said mobile unit; said reply means of said mobile unit replies said response signal to said on-vehicle unit every time when said mobile unit verification encryption code is received; and said control means of said on-vehicle unit updates and stores vehicle environmental information in the storage part of said on-vehicle unit every time when said on-vehicle unit receives said response signal, and, in the case where said on-vehicle unit cannot receive said response signal from said mobile unit, the notification means notifies the driver that the response signal has not been received.