| 摘要 |
PURPOSE:To provide a theft preventive device for car, which senses that the car encounters a theft attempt while no alarm will be emitted merely with approach of a pedestrian or a car passing by. CONSTITUTION:A photo-sensor 4 to sense the height from the road surface contactlessly is furnished on the inner surface of a panel of car body, and sensing signals therefrom are fed to a time duration judging means 10, and if it judges that light is blocked for more than a certain set time, an alarm signal emitting means 7 is actuated. It is so arranged that a portable receiving means 8 gives alarm upon receiving radio signal from this alarm signal emitting means 7. Thereby the driver can receive alarm in a place remote from the car if there is anything which blocks the light flux in the neighborhood of any tire of the stolen car or if the car body sinks with any person having got thereon and if, at the same time, the sensing signal given by the photo-sensor 4 exceeds the set time. Therein the sensing accuracy is enhanced because the photo-sensor 4 senses road surface or the shadow of a person and because blocking the light is taken up only when a certain long period of time has elapsed. |
