BURGLAR ALARM PHOTOELECTRONIC DEVICE Russian patent published in 1997 - IPC

FIELD: signalling systems indicating presence of intruder in dwelling houses, public and administration buildings. SUBSTANCE: burglar alarm has emitter, as well as tandem-arranged light filter, detector built around photocells and bandpass amplifier, threshold unit, and alarm unit. Novelty in device is compensating unit inserted between output bandpass amplifier and input of threshold unit. Compensating unit has series-connected compensating amplifier and storage-retrieval circuit whose output is connected through integrator to second input of compensating amplifier to form feedback circuit; first input of compensating amplifier connected to output of bandpass amplifier functions as input of compensating unit, and its output functions as that of storage-retrieval unit. EFFECT: provision for detecting only moving objects due to recording differential signal. 2 cl, 3 dwg