Abstract: A deactivatable electronic theft detection marker is made from a strip or ribbon of high magnetic permeability strip or ribbon and then high magnetic coercivity material is deposited on the strip or ribbon by electroplating.

Abstract: A responder for electronic article surveillance apparatus is made by subjecting a plurality of magnetizable elements to heating in the presence of a magnetic field and maintaining the field at a different intensity for each element as it is cooled to provide different magnetic characteristics so that when the responder is subjected to a cyclically varying magnetic interrogation field its several elements produce spaced apart pulses in each cycle.

Abstract: Signals received by an electronic article surveillance system are processed digitally to ascertain the variation in magnitude of successive signals and to prevent the actuation of an alarm when the variation exceeds a predetermined amount; and signals whose frequency components have been phase shifted from a filtering operation are restored by passing them into a signal delay circuit, tapping the delay circuit at several points therealong into associated signal channels selectively amplifying or attenuating the signal in each channel and combining the signals in each channel.

Abstract: Magnetically desensitized targets or sensor elements on protected articles are resensitized by means of rotating permanent magnets which are moved relative to the magnetized target desensitizer elements such that the elements become subjected to reversing magnetic fields of gradually decreasing intensity.

Abstract: An electronic article surveillance system responder which comprises an electrical responder circuit and a housing which mounts the circuit on an article to be protected. The housing is arranged to support the circuit in such a manner that a dielectric region is formed between the circuit and the article. An electrically conductive plate is also held by the housing on the opposite side of the dielectric region from the circuit to isolate the circuit from the effects of metal objects on which the responder is mounted. The housing is flared so that it can be mounted on an article in proper orientation.

Abstract: Items of merchandise (30) are protected from shoplifting or theft by affixing to them special responder targets (32), which are formed by drawing a material of high magnetic permeability into a thin wire and thereafter rolling the wire into a flattened strip and annealing the strip and severing the strip into individual lengths. The flattened strip may be positioned on an adhesively coated base strip (42) and covered by a peel strip (46). Slug-like deactivation elements (48) of hard magnetic material may be positioned along the strip for deactivating it.

Abstract: Articles of merchandise (42) which contain deactivatable theft detection targets (44) have their targets deactivated by passing them through a box-like apparatus (30) made of low coercive force, high saturation induction material with a multiplicity of permament magnets (48) on its inside surfaces so as to generate magnetic fields which extend at different directions and at decreasing intensities from one end of the apparatus to the other so that irrespective of a target's orientation while passing through the apparatus, the target's magnetic deactivation slugs or elements will encounter a magnetizing field along the target's length sufficient to magnetize the elements.

Abstract: An electronic theft detection system with a transmitter antenna assembly which includes a flat electrically conductive panel positioned close to a transmitter loop antenna to preload it and isolate it from the loading effects of nearby metal objects and a receiver arranged with a signal gate synchronized to the transmitter antenna energization to prevent detection of targets located on the opposite side of the panel from the transmitter loop antenna.

Abstract: A fastener and fastener assembly characterized by a pin with an expansive molded plastic head of concave configuration and a frangible membrane sealed to the head to enclose a hollow space for containing an undesirable fluid such as a dye, so that when prying forces are applied to bend the head, the membrane is stressed and shatters to release the dye.

Abstract: A novel sensor element having low magnetic coercivity and an asymmetric hysteresis characteristic is formed by heating a strip of cobalt alloy in an exidizing atmosphere to form an oxide coating thereon and then the strip is cooled in the presence of a magnetic field of about 0.3 oersteds along its length. The strip is detected by subjecting it to an alternating magnetic interrogation field and passing the resulting magnetic disturbances through signal processing circuits which select pulses produced only once in each interrogation field cycle. The element is deactivated by subjecting it to a magnetic field which eliminates its asymmetry.

Abstract: A magnetically releasable pin lock which comprises catch elements mounted to pivot about axes perpendicular to and displaced from the pin axis and elongated magnetizable actuation elements which extend from the catch elements along the pin axis to be acted upon by applied magnetic decoupling fields and to move in response to such fields to pivot the catch elements and release the pin.

Abstract: A swept frequency theft detection system for detecting different resonant circuit targets which are resonant at different frequencies. The system comprises arrangements to generate swept frequency transmitter signals centered at different frequencies but which are swept in synchronism. Also provided are antennas formed by offset loops, with the loops of different frequency antennas lying along different diagonal lines.

Abstract: An article surveillance system includes a first monitor 26 at a store exit way 12 and second monitors 34 in the dressing rooms 20 and rest rooms 22 in the store to detect security tags 24 attached to articles of merchandise 14. When the tags 24 are attached to the merchandise they hold a ring 82 against the tags causing them to have a high resonant frequency which is detected by the first monitors 26 but not the second monitors 34. If the tags are removed from the merchandise in a dressing room or rest room, the ring falls away from the tag and its resonant frequency lowers and the tag is then detected by the second monitor 34.

Abstract: A deactivator for deactivating targets used in electromagnetic article surveillance systems comprises a solid element with a convexly curved outer surface, e.g., a cylinder and a plurality of permanent magnets which form a patter of variously directed magnetic fields is a plane adjacent the surface. The curved surface of the deactivator is rolled over a target to be deactivated. The magnets are also arranged in adjacent layers with the magnets of one layer extending in a different direction from the magnets of the other layer to form a composite magnetic pattern which is discontinuous in all directions.

Abstract: Targets (14) mounted on objects (12) for detection by a magnetic type theft detection system are deactivated in a target deactivator (26,64) which has magnet assembly (40,72) made up of spaced apart magnets with alternately opposed poles extending in a plane and guide walls (36, 38, 68, 70) extending perpendicular to the plane. Targets are reactivated by a reactivator (46, 76) having a magnet (52, 80) mounted thereon and arranged to be slid along the target.

Abstract: A self contained electronic theft detection apparatus comprising a housing (30) from which a rigid tubular transmitter antenna loop (32) extends; and a wire loop receiver antenna (56) extends inside the transmitter antenna loop. The transmitter antenna (32) is provided with a capacitor (C54) with which it resonates at the frequency of responder elements to be detected and the transmitter antenna is supplied with sharp voltage pulses from a pulse forming circuit (66) and a power amplifier (68) which cause the antenna to resonate in a rapidly decaying manner.

Abstract: Targets (30) of readily saturable mangetic material and mounted on protected articles (14) are detected when taken through an interrogation zone (24) in which an alternating magnetic interrogation field is generated by transmitter antenna coils (42, 44). The target (30) is driven alternately into and out of saturation and it disturbs the alternating magnetic interrogation field in a manner so as to produce alternating magnetic fields at frequencies which are harmonics of the frequency of the alternating magnetic interrogation field. The composite of these alternating magnetic fields has a characteristic asymmetry due to the effect of the earth's magnetic field. The target responses are detected by receiver antenna coils (50, 52) to produce first detection signals which are processed in a compressor (118) and a signal averager (124) to produce asymmetry signals which are compared in a comparator (146) with the first detection signals to produce alarm signals.

Abstract: A tamper-resistant target wafer (10) for use in an electronic theft detection system has a housing formed with bulges (16 and 22) aligned with each other on opposite sides and which slope continuously downward toward the plane of the target wafer to minimize fulcrum leverage to a prying tool and to enclose a locking mechanism (38) in a manner such that it is protected from attack by plier-like tools.

Abstract: Items of merchandise (30) are protected from shoplifting or theft by affixing to them, special responder targets (32), which are formed by drawing a material of high magnetic permeability into a thin wire, then heat treating the wire to substantially increase its magnetic permeability and thereafter severing the wire into individual lengths. Several wires (32a, 32b and 32c) may be positioned on a common adhesively coated base strip (42) and covered by a peel strip (46) and wire like deactivation elements (48) of hard magnetic material may be positioned adjacent the wires for deactivating them.

Abstract: A fastening assembly for fastening a wafer (10) to an article of merchandise (12) and comprising a locking mechanism in a housing (14) and a fastener element (16) having an expansive head (18) and a shank (20), formed with axially spaced circumferential grooves 22 for releasable locking engagement with a locking mechanism, the head having a conical exterior with an apex angle less than ninety degrees so that if the fastener element should fall onto a flat surface, the shank will slant upwardly less than forty five degrees; and downward pressure on the tip of the shank will cause it to tilt downwardly safely and without appreciable resistance.