Anti-theft device using transmission of electromagnetic waves

摘要

The battery-powered transmitter (K1) integrated e.g. into the ignition key (2) of a motor car (1) radiates at 10-second intervals a signal (B) encoded jointly by the owner, insurance company and monitoring service.Within a range of 50 m., a transponder (K2) concealed in the vehicle detects the transmitted signal and sends a encoded message (S) over another channel (3.2) to a monitor (K3) at a frontier checkpoint (4) which may be up to 30 km. away. If the vehicle is taken out of range of the transmitter (K1), the message is changed to one indicating its theft.