System and method for detecting unauthorized removal of goods from protected premises, and magnet detecting apparatus suitable for use therein

Abstract

Abstract An improvement in systems in which a clip containing a magnet is secured to goods in a store, and in which magnet-sensing means are provided at an exit from the store to give an alarm if one attempts to remove the goods through the exit with the magnetcontaining clip still attached; in an authorized removal of the goods, e.g. pursuant to a purchase, the goods with clip attached are taken to a check-out counter where the attendant removes the clip and magnet so the goods can be removed through the exit without sounding the alarm. The improvement comprises a mat-like array of loops of conductor coils disposed flat along a surface of the counter adjacent the attendant, over which array the goods are moved by the attendant in the course of the check-out procedure. If a magnet-containing clip is still attached to the goods, the motion of the magnet will induce currents in the coils to operate an indicator telling the attendant of this fact. If the attendant has failed to find and remove a clip from goods during the check-out procedure, the latter indications will so warn the attendant; upon observing the indication, the attendant then finds and removes the clip and magnet. This eliminates the possibility that the innocent purchaser may be embarassed by causing an alarm when he attempts to remove his purchases through the store exit. Preferably the coil array comprises at least two separate conductor loops of similar configuration, overlapping each other but spacially displaced in a horizontal plane, so that the moving magnet will induce currents in the loops; however the effects of simultaneous similar changes in magnetic flux through the two coils such as may be produced by changes in stray magnetic fields are cancelled out, and do not operate the indicator.

Inventors

• 👤 Allan L Williams
• 👤 Lyle D Heck

Bibliographic Details