Apparatus for detecting theft by a radio wave

摘要

A burglar detection apparatus has a tag 11 that includes a resonance circuit. The tag is preferably contained with an object 15 whose theft is desired to be detected. The tagged object may be placed in a drawer 14 which is contained in a box 13. A tag detection sensor 16 is installed in the box and detects whether the tag 11 is present in the drawer 14. Also, a drawer sensor 17 detects whether the drawer is opened. Based on respective detection outputs of the tag detection sensor 16 and the drawer sensor 17, a control circuit 19 controls an alarm 18. Advantageously, the apparatus can be installed in a comparatively small space, does not malfunction even if subjected to large amounts of electrical noise, and reliably detects the presence or absence of a tag even if the tag is located near a metal object.