Article surveillance system having target removal sensor

Abstract

An article surveillance marker includes a marker body having two sections connected together by a resilient hinge. A securing pin holds the body sections together in a closed position and secures the marker to an article to be protected. Two ferromagnetic ribbons are housed within separate cavities in the marker body. The first ribbon is free to mechanically vibrate and produce a first signal in response to an applied interrogation field that indicates the conveyance of the protected article from an authorized area. A contact button on the marker body damps and deactivates the second ribbon when the marker body sections are closed and the marker is secured to the article. Specifically, the contact button extends through an aperture in the marker body that communicates with the cavity containing the second marker ribbon. When the marker is closed, the button engages the second ribbon and prevents mechanical vibration and, therefore, the production of a second response signal. Conversely, when the marker is opened, the contact button disengages the second ribbon that is then free to vibrate mechanically and produce a signal indicating the unauthorized opening and removal of the marker from the article. A complete article surveillance system including a marker and two interrogation and detection circuits is also provided.