Abstract: A coherent frequency, velocity responsive electronic surveillance system detects the motion of a transponder relative to two receiving antennas on opposite ends of a surveillance zone positioned at the exit of a retail store. Motion in opposite directions relative to the two antennas indicates that the transponder is within the surveillance zone. As a means of reducing false alarms, motion of a transponder proximate to, but outside the zone is distinguished from motion inside the zone because motion outside the zone is in the same direction relative to both antennas. False alarms are reduced even further by requiring detection of motion through a selected distance before indicating an alarm.

Abstract: A time limited coherent frequency doppler radar system monitors a precisely bounded merchandise detection zone for motion of a transducer therein. False alarms are reduced without limiting sensitivity by limiting the maximum radar signal propogation times to control the outer boundaries of the detection region and by requiring a selected minimum motion within the detection zone. An even more precisely bounded merchandise surveillance zone can be realized by using two spaced-apart radar systems having overlapping detection zones.

Abstract: A reusable, pneumatically releasable security tag for monitoring merchandise such as a garment, is disclosed. Encapsulated within the tag is a transponder element which reradiates a radio frequency signal to trigger an alarm when a tagged article is carried through a surveillance zone. The tag includes a housing concealing a one-way latch spring fastener for receiving and gripping the shank of a tack inserted through the garment and into the housing. The housing defines a chamber sealed by a generally horizontally oriented diaphragm adapted to be deflected by pressurized air admitted into the chamber through a small inlet. An actuator interposed between the diaphragm and the latch spring fastener is adapted to engage and deflect the fastener to a tack-releasing configuration upon the admission of pressurized air into the chamber.A resilient pad may be inserted under the head of the tack.

Abstract: A releasable, reusable, tamperproof device for attaching an anti-theft monitor to an article of merchandise is disclosed. The attachment device includes a tack adapted to be passed through the monitor and the article and into a keeper. The keeper encloses a one-way fastener of the type having opposed legs defining surfaces for gripping the pointed shank of the tack. Compression of the opposed legs to a releasing position permits withdrawal of the tack. In accordance with one embodiment, the keeper includes openings through which rotatable key means are insertable for engaging and displacing the legs to the tack-releasing position. In another embodiment the keeper incorporates flexible diaphragms dividing the keeper into a pair of side chambers separated by a central chamber enclosing the one-way fastener. Pressurization of the side chambers deflects the diaphragms into engagement with the fastener legs and causes displacement thereof to the tack-releasing position.

Abstract: A releasable, reusable, tamperproof device for attaching an anti-theft monitor to an article of merchandise is disclosed. The attachment device includes a tack adapted to be passed through the monitor and the article and into a keeper. The keeper encloses a one-way fastener of the type having opposed legs defining surfaces for gripping the pointed shank of the tack. Compression of the opposed legs to a releasing position permits withdrawal of the tack. In accordance with one embodiment, the keeper includes openings through which rotatable key means are insertable for engaging and displacing the legs to the tack-releasing position. In another embodiment the keeper incorporates flexible diaphragms dividing the keeper into a pair of side chambers separated by a central chamber enclosing the one-way fastener. Pressurization of the side chambers deflects the diaphragms into engagement with the fastener legs and causes displacement thereof to the tack-releasing position.