Minnesota Mining and Manufacturing Company

3m Innovative Properties Company

Bibliotheca Rfid Library Systems Ag

Dean M Dowdle

Michael E Hamerly

William C Egbert

Ziyad Hanna Doany

Terrence H Joyce

Gary E Nourse

Ronald David Jesme

An article, system and method related to a magnetomechanical marker used to mark stationary assets. Magnetomechanical markers can be arranged in clusters and associated with stationary assets, including assets buried underground. Markers can be associated with an asset by being attached to the asset, arranged in a particular spatial relationship with the asset, or in any other appropriate way. A portable locating device can be used to generate an alternating magnetic field to activate the magnetomechanical marker and thus locate the asset.

Magnetomechanical markers for marking stationary assets

A single turn loop electronic article surveillance (EAS) gate. The gate includes a closed magnetic core, a multi-turn primary winding wound around the core, and a secondary loop passing through the core once. The secondary loop is a self-supporting single turn loop, and the secondary loop is a transmit loop that generates a magnetic drive field for the article detection gate system.

Single turn magnetic drive loop for electronic article surveillance

An electronic article surveillance system is disclosed, having a transmitter means for producing in an interrogation zone sequences containing a plurality of discrete different radio frequencies thereby causing a circuit present within the zone to resonate at its resonant frequency in response to energy absorbed at at least three different frequencies. A receiver means is provided to cause an alarm in the event of detection of three such resonances over two successive sequences.

Variable frequency RF electronic surveillance system

A shielded, closely spaced transmit-receiver system for use in an electronic article surveillance system is disclosed wherein at least one of the antennas is provided with at least two twisted loops lying in a common plane each loop being twisted 180.degree. to be in phase opposition with the adjacent loop and wherein both antennas are substantially enclosed by a conductive shield having a discontinuity in an outer portion enclosing each of the twisted loops.

Growing community of inventors

White Bear Lake, MN, United States of America

Dean M Dowdle