Radio detection system protecting shop wares - has transmitter in supervised zone behind cash desk and tuned circuit on object removed by key on purchase

摘要

The wares to be protected against theft are fitted with an oscillating circuit consisting of a coil and capacitor tuned to the supervising transmitter frequency. This circuit is locked and can only be removed without damaging the goods by the cashier's key. It is removed at the cash deck. The supervised zone is situated in front of the exit and any tuned circuits still in place respond to the transmitter's radiation. This energizing is detected by a receiver within the supervised zone. The increase the magnetic field and reduce the size of the tuned circuit coil (13) a ferrite core (15) is provided. A boring (16) in the middle is used to fix the core (15) within the housing.