MULTI-PHASE MODE MULTIPLE COIL DISTANCE DEACTIVATOR FOR MAGNETOMECHANICAL EAS MARKERS

摘要

A device for deactivating a magnetomechanical electronic article surveillance marker includes first, second, third and fourth rectangular coils arranged in a two-by-two array in a common plane. Drive circuitry energizes the coils according to an operating cycle which includes three modes. In the first mode, all four coils are driven with respective alternating currents in phase with each other. In the second mode, the first and second coils are driven in phase with each other and the third and fourth coils are driven substantially in phase with each other and substantially 180 DEG out of phase with the first and second coils. In the third mode, the first and third coils are driven in phase with each other and the second and fourth coils are driven in phase with each other and 180 DEG out of phase with the first and third coils. Taking into account the three modes of operation, substantial magnetic fields are generated in each of three mutually orthogonal directions so that a substantial deactivation field is provided along the length of the marker to be deactivated, regardless of the direction of orientation of the marker relative to the coil array. Two-coil and quadrature-driven deactivators are also disclosed.