Abstract: A display may have a pixel array such as a liquid crystal pixel array. The pixel array may be illuminated with backlight illumination from a direct-lit backlight unit. The backlight unit may include an array of light-emitting diodes (LEDs) on a printed circuit board. The display may have a notch to accommodate an input-output component. Reflective layers may be included in the notch. The backlight may include a color conversion layer with a property that varies as a function of position. The light-emitting diodes may be covered by a slab of encapsulant with recesses in an upper surface.

Abstract: A system for monitoring the occurrence of an event occurring with respect to an essentially metallic enclosure such as a truck body, e.g., the unwarranted opening of a locked door to the enclosure, which comprises a detector within the enclosure which senses the occurrence of the event and radiates a spread spectrum signal which is readily received by an external module mobile relative to the enclosure, so that the enclosure, at any time during its active life, may be externally interrogated to ascertain whether any such event has occurred, the enclosure optionally also containing a separate unit which records the spread spectrum signals for subsequent display and analysis, whereby the security status of the enclosure may be externally monitored at will, thereby to indicate whether or not the enclosure has been tampered with and, optionally, its security history--when and how frequently the event has occurred--may be retrieved.

Abstract: The security of articles, and particularly articles in transit, is checked by detecting the status of a magnetic strip attached to the articles at a strategic location when the strip is subjected to an electromagnetic field which causes the strip to substantially saturate magnetically, the status of an improper strip, that is to say, a strip whose electromagnetic properties differ from those of a proper strip as a result of physical modification or disparity, being reflected in the nature of the electromagnetic field emanating therefrom, detection of the status of that field providing an indication of whether the strip is proper or not. The same principles can be applied to the coding of articles for validation of identity or authenticity.

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 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 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: 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 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: In an electronic theft detection apparatus the passage of a resonant circuit wafer 16 through an interrogation zone formed by transmitter and receiving antennas (30, 90) (32, 92) is detected by generating sharp pulses of electromagnetic energy to cause the resonant circuit wafer to resonate for a duration following each pulse. A receiver is provided with a switch (54), signal accumulators or filters (56 and 58) and a comparator (60) to sense the decay of the signal from the resonating wafer and to activate an alarm (36) when that decay occurs at a predetermined value.

Abstract: An electronic theft detection apparatus for detection of saturable magnetic targets has transmitter and receiver antennas formed of single turn loops of rigid metal pipe. The antennas are rectangular and have a width, in the direction of passage, through the interrogation zone, less than the length of a shopping cart. The transmitter antenna is in the form of a rectangular loop and the receiver antenna is of the same overall size and configuration but is bisected with a conductor to form two balanced loops. The antennas are purely inductive and a series resonant circuit is inductively coupled into the transmitter antenna and a parallel resonant circuit is inductively coupled out of the receiver antenna. Special circuits are also provided for temporarily disabling the apparatus when a related lower harmonic frequency signal decreases in amplitude.

Abstract: An electronic article theft detection system accurately senses the presence of a target on a protected article by sensing electromagnetic disturbances at a plurality of frequences, comparing their relative amplitudes and producing a detection signal when the compared relative amplitudes correspond to those produced by the presence of a target.

Abstract: An article theft detection system for identifying which of two adjacent passageways a protected article passes. Each passageway is provided with spaced apart interrogation and receiver antennas, but a single receiver antenna services both passageways. Multiplexing is used to energize the interrogation antennas in alternate sequence. The single receiver antenna is connected to a single receiver whose output is connected through switches, synchronized with the interrogation multiplexing, to separate alarms for each passageway.