| 摘要 |
The present invention relates to an alarm system comprising a volumetric ultrasound detector intended for motor vehicles. The alarm system control circuit comprises a means for adapting the width (t1) of a square wave pulse used to activate the ultrasound emission circuit in such a way as to minimise power consumption. In the same way, the square wave pulse (R) for activating a reception circuit falls within the evanescent wave, so that the transducers operate alternately. Furthermore, the control circuit auto-adapts the alarm system to the acoustic conditions of the volume under surveillance by, in particular, adjusting the width (t1) of the square wave pulse used to activate the ultrasound emission circuit. Application to motor vehicle alarm systems. <IMAGE> |
