DEVICE FOR DETECTING AN INTRUDER IN A BUILDING OR VEHICLE BY INFRASONIC AND/OR PRESSURE WAVE DETECTION AND METHOD FOR SO DETECTING AN INTRUDER

摘要

Device for detecting an intruder in a building (1) comprising an infrasonic sensor (6) located outside the building, and an infrasonic sensor (4) located inside the building. The device further includes means for dividing the absolute value of the amplitude of a signal supplied by the inside sensor (4) by the absolute value of the amplitude of a signal from the outside sensor (6) after being analyzed and then temporally processed by signal integration. A threshold circuit receiving the signal from the division means detects threshold crossing of the signal from the division means. Means for storing threshold crossing briefly holds the threshold signal. Means for measuring the temporal shift between the signals from both sensors provides a measurement of said shift to an alarm decision means connected to the storage means. The alarm decision means provides, according to the temporal shift measurement, an alarm signal if the storage means provides a threshold crossing signal.