Minnesota Mining and Manufacturing Company

Gary E Nourse

Dean M Dowdle

Peter J Zarembo

James E Fergen

Operation of similar electronic article surveillance (EAS) systems in proximity to each other may result in false alarms or system 'shut-downs' as a result of signals transmitted from one system being detected in the receiver circuits of the other systems. This may especially occur with EAS systems in which the receivers are only activated during quiescent intervals between transmitted bursts, such that if the systems are unsychronized, the transmitted bursts of the one system may occur during the quiescent intervals of the other system. In the present invention, synchronization is effected by responding to RF detected during the quiescent intervals and preventing the transmitted bursts from occurring during the quiescent intervals of the other system.

Wireless synchronization system 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.

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Osceola, WI, United States of America

Gary E Nourse