Movement detector for burglar alarm system - is combined with range measuring system for monitoring detector position, to prevent sabotage

摘要

The movement detector uses an ultrasonic or microwave Doppler effect, or a passive IR radiation detection system. the movement detector is combined with a range measuring system monitoring the distance between the detector and a surface or object in the main detection direction. The movement detector and range measuring device are identical. The range measuring system is operated each time the alarm system incorporating the movement detector is switched on, with a fault signal supplied when the measured range differs from the required value. USE/ADVANTAGE - Prevents sabotage of movement detector by screening its field of view.