Electronic Article Surveillance (EAS) and Shoplifting

How Magnetic Strip Alarms Work

Modern retail outlets use a variety of ways to deter shoplifters, and more and more, magnetic strip alarms (known as electronic article surveillance systems, or EAS) are becoming common and accepted business practices. EAS tags are put on products in the store, and when the item is checked out the tags are deactivated by store staff before the item is removed from the store. If the item leaves the stores through the exits before it has been deactivated, the alarm on the system sounds.

Types of Electronic Article Surveillance Systems

There are several types of EAS systems, although the magnetic is one of the most common. Acousto-magnetic, also known as magnetostrictive, is similar to the standard magnetic tag system of shoplifting deterrence but has two strips. These systems are thick and seldom used for books, unlike magnetic systems, but they are relatively better at detection (fewer false positives and negatives) than magnetic tags. Other EAS systems include radio frequency, microwave and video surveillance.

Magnetic Strip Alarms

Magnetic strip alarms are made of amorphous metal, which has a very low magnetic saturation value. The strip is lined magnetic material with a moderate magnetic "hardness." Detection occurs when sensing harmonics and signals generated by the magnetic response of the material under low-frequency magnetic fields. When the ferromagnetic material is magnetized, it forces the amorphous metal strip into saturation. In other words, when clerks and store staff demagnetize the tags, they are actually magnetizing them; detection occurs when the amorphous metal is demagnetized, and therefore can be detected by the lack of magnetic response produced by the low-frequency field.