| 摘要 |
PURPOSE:To eliminate danger that a vehicle already collides against a body when detection and display operation is performed by starting detecting operation when the speed of a vehicle reaches below a set speed and starting detection and display operation when the speed decreases below the set speed. CONSTITUTION:For example, the vehicle which travels at a high speed is braked and the vehicle seed decreases below a vehicle speed Vg where the detection operation is started. This vehicle speed is detected by a vehicle speed calculation part 2f and a detecting operation control part 2g allows a detection operation block 21 to start operating, thereby performing plural rotation detecting operation. When the vehicle speed further decreases below a vehicle speed V1, the vehicle speed calculation part 2f detects the speed reaching the speed where the detection and display operation is started and a detection and display control part 2h makes a detection and display block 22 ready to receive the output of the detecting operation block 21. Namely, the detecting operation is started at a point t1 of time when the vehicle speed reaches the slow vehicle speed as usual and then the detecting operation is performed at least three times from t1, but the detecting operation is started at a point t0 of times in this case and the operation of an alarm 6 is not delayed.
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