Abstract: The present invention discloses: an antenna for detecting a magnetic field, wherein a plurality of loop antennas wound in opposite directions are connected in series and placed in a plane, a magnetic field detector comprising a plurality of the above antennas for detecting a magnetic field and an output circuit for taking out a differential output between the outputs of the plurality of antennas, and a gate for detecting detection tag comprising the above magnetic field detector and a coil for magnetic field generation.

Abstract: The present invention discloses a decision machine of detection tag using magnetic field, comprising: a cross coil 22 constituted by a plurality of individual coils which have been wound round a frame member so as to form a predetermined differential angle between the central axes of the individual coils, a magnetic power supply part 24 comprising an oscillator for generating an AC power and a phase modulator for differing each other the phase of AC power generated by the oscillator, by a predetermined differential angle, to supply powers of different phases to the individual coils, a signal processor part 28 connected to the plurality of individual coils, and a decision part 30 for deciding the output signal sent from the signal processor part.

Abstract: A magnetic detection-tag deactivating apparatus for deactivating a magnetic detection-tag, having preferable operability when deactivating operation, and further enabling to increase accuracy of deactivation, includes: at least one or a plurality of deactivating rollers, disposing one or more cylindrical unitary permanent magnets, on a periphery surface of which is magnetized to N-pole and/or S-pole, along an axial direction thereof, whereby deactivating the magnetic detection-tag through a relative movement between the magnetic detection-tag and the deactivating roller. Herein, it is preferable that the deactivating roller is provided in rotatable manner.

Abstract: The present invention discloses a method for reactivating a magnetic detection tag, which comprises exposing a magnetic detection tag having a soft magnetic substance layer and a hard magnetic substance layer, to an alternating magnetic field generated by applying an AC power to a coil, moving, in this state, either or both of the magnetic detection tag and the alternating magnetic field, thereby sweeping the magnetic detection tag in the alternating magnetic field to demagnetize the magnetized hard magnetic substance layer of the magnetic detection tag; and a machine for reactivating a magnetic detection tag.

Abstract: A compact magnetic object detection device with high degree of freedom for installation can be provided. The magnetic object detection device includes magnetic field generating mechanism for radiating an alternating magnetic field in a vicinity space; one or a plurality of loop antennas which convert the magnetic field in the vicinity space into an electric signal; determining mechanism for analyzing an existence of magnetostriction and determining an existence of a magnetic object, the magnetostriction generated by the magnetic object existing in the vicinity space based on the electric signal of each of the loop antennas. An installation member, attached with at least the magnetic field generating mechanism and each of the loop antennas, has a pole shape.