Abstract: A merchandise tagging technique includes a transmitter and receiver module, called hereinafter the interrogator, located at the merchandise inspection point. When a piece of merchandise containing an activated tag passes in the vicinity of the interrogator, an alarm signal occurs. The transmitter produces a pulsed magnetic field which excites the tag. The magnetic oscillations produced by the tag are detected by the receiver-each tag magnetic burst being coherently accumulated.The tag is a small, passive, magnetically-permeable core with a winding on it which results in a self resonant structure that produces magnetic oscillations when excited by the transmitter. These oscillations are detected by the receiver and processed for optimal enhancement during the residence time of tagged merchandise passing by the interrogator. The tags can be small and mass-produced at low cost, which makes this scheme an economically valuable technique.