ANTITHEFT SIGNALLING DEVICE WITH DETECTION OF MARKS Russian patent published in 1995 - IPC

FIELD: alarm signalling. SUBSTANCE: antitheft signalling device has two aerials - radiating 5 and receiving 8, high-frequency amplifier 9, generator 3 of rectangular pulses, synchronous detector 11, integrator 12, threshold detector 13 and indicator 14 connected in series. Frequency-modulated generator 1 is linked to output of generator 3. Antitheft device is inserted with directional coupler 4, delay line 6, multiplier 7 and band-pass filter 10 connected to input of synchronous detector 11. Multiplier 7 is coupled to output of high- frequency amplifier 9, directional coupler 4 is linked to input of radiating aerial 5 and to output of frequency-modulated generator. Insertion of directional coupler 4 and multiplier 7 enables tuning of radiating signal and of receiver to be ensured. EFFECT: increased authenticity and range of detection of marks. 1 dwg