Abstract: An electronic article surveillance system which is capable of reliably identifying and discriminating between the different signatures of tags and labels which may come to pass in its vicinity, improving the reliability of the system and even permitting the tags and labels to be classified by type, and separately addressed, includes a receiver for detecting signals resulting from such tags or labels which incorporates improvements in its filtering and processing sections. A linear phase (constant group delay) filter is used to more effectively preserve the signal which is received, and thereby improve the signal which is ultimately delivered to the processor which follows.

Abstract: To reduce the occurrence of false alarms, the disclosed system incorporates an auxiliary sensor for detecting the presence of a shopper passing through the electronic article surveillance device, such that the device is operated continuously, and the auxiliary sensor is used to enable external alarms of the device only upon detecting the shopper's presence. Thus, while the device continuously monitors field-induced signals which are received, activation of the external alarm is permitted only when a shopper passes through the security device and is detected by the auxiliary sensor. Sounding of the alarm is then based upon an analysis of the data received at and just prior to the detected approach of the shopper to be monitored, eliminating phantom alarms while significantly reducing false alarms and merchandise-activated alarms.