Short-range radio device for detection of stolen vehicle - broadcasts modulated signal indicating unauthorised driving, for reception and demodulation by receiver operated by law enforcement agency

摘要

An antenna (22) on the vehicle radiates a high-frequency signal (30) from a transmitter (12) incorporating a carrier-frequency oscillator (16) and frequency modulator (18), triggered by an activator (24) connected to the ignition switch (26) and/or a manual tuner (28). If the vehicle is broken into and driven away, a receiver (14) installed in, e.g. a police car or frontier post, can detect the radiated signal at a range of the order of 100 to 200 m, and generate a visual and/or audible warning (40) in time for the stolen vehicle to be intercepted. USE/ADVANTAGE - Esp. in motor vehicle, radiated alarm signal is not liable to be disregarded (like an oversensitive acoustic alarm) but is reliably effective in event of theft.