Abbreviated EAS, it refers generically to the placement of tags on
articles in a store to detect whether they are leaving the store. Typically these tags are deactivated when the article is purchased, so that detection is coincidental with
theft. Garment sales comprised the bulk of the original market for EAS, thus the use of the term '
article'; today, EAS tags are often used on other
consumables and
commodities.
One system of EAS uses an
amorphous allow with soft
magnetic properties to create a strong
electromagnetic signal when exposed to an alternating electromagnetic field provided by a gate at the exit to the store. An accompanying strip of magnetizeable material can be magnetized upon purchase, thus negating the signal production at the gate.
Another system prints a miniature
LCR circuit onto a sticker. When exposed to electromagnetic radiation at the natural frequency of the tag the resonance thus created emits a strong detectable signal.