Multi-system antitheft system e.g. for safe - combines Doppler radar volumetric detector, ultrasonic detector acoustic sensor and alarm condition transmission circuit

摘要

The system includes a microwave Doppler radar volumetric detector (1), and an acoustic detector (2) which comprises a microphone (3) associated with a signal amplifier (4) feeding into a passband filter (5) and processing circuit (6). A further detector uses ultrasounds to detect any attempted masking of the detectors, a receiver (8) normally receiving a small part of the energy radiated by an ultrasound transmitter (7). If the reflected energy changes, the detector senses the variation. The different sensors are electrically connected to a logic circuit (10) processing their signals, and interfacing with an alarm (12). An electrical supply (11) comprising batteries and a charger ensure the independent operation of the alarm if the mains supply is cut.