How Anti-shoplifting Devices Work? How EAS devices can detect security tags and security labels?

The most effective anti-shoplifting tools these days are tag-and-alarm systems, better known as electronic article surveillance (EAS) systems. Separately, these are good options. Used together, experts say, they're almost unbeatable. EAS is a technology used to identify articles as they pass through a gated area in a store. This identification is used to alert someone that unauthorized removal of items is being attempted. According to the Association of Automated Identification Manufacturers, over 800,000 EAS systems have been installed worldwide, primarily in the retail arena. EAS systems are useful anywhere there is an opportunity for theft of items of any size. Using an EAS system enables the retailer to display popular items on the floor, where they can be seen, rather than putting them in locked cases or behind the counter.
New EAS technologies are being produced -- not only to reduce shoplifting -- but also to help increase sales, lower labor costs, speed inventory, improve stockroom logistics and, one day, to replace inventory record-keeping. But for now, we'll stick to the role of EAS in battling shoplifting in your imaginary store!
Three types of EAS systems dominate the retail industry. In each case, an EAS tag or label is attached to an item. The tag is then deactivated, or taken from an active state where it will alarm an EAS system to an inactive state where it will not flag the alarm. If the tag is a hard, reusable tag, a detacher is used to remove it when a customer purchases the item it's attached to. If it's a disposable, paper tag, it can be deactivated by swiping it over a pad or with a handheld scanner that "tells" the tag it's been authorized to leave the store. If the item has not been deactivated or detached by the clerk, when it is carried through the gates, an alarm will sound.
The use of EAS systems does not completely eliminate shoplifting. However, experts say, theft can be reduced by 60 percent or more when a reliable system is used. Even when a shoplifter manages to leave the store with a tagged item, the tag still must be removed -- something that is no longer as easy as it once was. For example, some EAS tags contain special ink capsules, which will damage the stolen item when forcibly, and illegally, removed. (This type of device is known in the industry as benefit denial -- we'll discuss it more later!). Other popular EAS components today include source tagging, whereby an inexpensive label is integrated into the product or its packaging by the manufacturer.
The type of EAS system dictates how wide the exit/entrance aisle may be, and the physics of a particular EAS tag and technology determines which frequency range is used to create a surveillance area. EAS systems range from very low frequencies through the radio frequency range (see How Radio Scanners Work). These EAS systems operate on different principles, are not compatible and have specific benefits and disadvantages. (That's why the Consumer Products Manufacturers Association, Inc. is encouraging a "tower-centric" EAS approach that can "read" multiple tag technologies rather than the "tag-centric" models that exist today.