About Electronic Article Surveillance
Electronic Article Surveillance, or EAS is a term used for theft prevention commonly used in libraries and most often, in retail stores. All types of items can be tagged with EAS tags and a few different types of form factors are available.The most common are pins through the item, labels attached to the item’s tags, and wire loops attached to the item. In each of these systems, all items are tagged with an EAS security tag upon being received in the store and must be deactivated upon purchase. EAS-enabled stores have gate readers at the entry/exit points that generate a field around the area to detect EAS transponders that have not been deactivated.
A few different types of EAS systems are available for use in order to prevent theft. The main ones are Electro-Magnetic, Acousto-Magnetic, and RFID. In all cases, pedestals at the front create a read field and when the tagged items move into the read field, they create a disturbance that is then picked up by the readers to raise an audio-visual alarm.
EM tags are built with two strips of metal and are activated by demagnetizing them. When these tags enter the low-frequency, electromagnetic field created by the two pedestals, the tag’s characteristics change, causing the tags to “harmonize” or make a sound that is picked up by the transmitter due to the frequency of the harmonics. When the pedestals pick up the harmonics from the tag, an alarm is sounded.
When the tag is deactivated by magnetizing it, it no longer harmonizes when subjected to magnetic fields and can be taken from the store. These systems are low cost and the tags can be deactivated and reactivated whenever needed. EM systems are ideal for applications that rent items to customers like libraries, or DVD/CD rentals.
Similar to EM systems, Acousto-Magnetic systems, or AM systems, send frequency waves in pulses in order to energize the tag so that it will respond. The tag sends a frequency signal back to the transmitter/receiver similar to a tuning fork. Instead of the tag’s response harmonizing like in EM systems, AM tags send a response at the same frequency as the transmitter which is received via a narrow band receiver in between the reader transmissions.
AM tags can be reusable plastic tags or disposable labels and are activated by magnetizing them – the opposite of EM tags. AM systems are sometimes preferred by retail stores because they receive less false alarms and they can be disposable.
RFID (8.2 MHz+)
Radio Frequency IDentification, or RFID systems, can also be used for security or theft prevention just like EM and AM systems. The RFID tags contain a wire coil (usually aluminum) as well as a capacitor and inductor which enables the tag to store energy until it reaches the frequency needed for transmission. The RFID reader or transmitter sends out RF waves and the RF EAS tags receive the energy and quickly pass it back and forth down the coil in order to build up enough energy to respond. A wideband receiver receives the response when the tag is in between or extremely close to the pedestals.
The number of coils and size of the RF EAS tag determine the available read distance between the tag and pedestals, which is usually a few feet. RF EAS tags are available in both plastic, reusable tags, and disposable label tags.
What are the Key Differences?
The biggest difference between RFID EAS and AM and EM EAS is that RFID tags contain a unique identifying number on them allowing the tags and therefore tagged items to be distinguished from one another. If an RFID EAS tag is picked up by the receiver or antenna, and software is deployed, a store associate can see exactly which item is being taken from the store. While identifying the item doesn’t necessarily help during the theft, it can be a time saving asset post-theft, which is why RF systems (in higher frequencies) are typically seen in inventory management applications.
- EM and AM systems are deployed solely to trigger an alarm during theft, and have no memory or item number contained within them like RF tags.
- AM EAS specifically has a lower rate of a false alarms, which is a key selling point to some retails stores because over time alarms could be ignored if thought to be fake.
- EM EAS is the least common system deployed among retail stores, but is the most common for libraries because of the simplicity of activating and deactivating.
- RF EAS is the most popular in retail stores because it has the lowest installation cost and per tag cost for disposable labels and also can assist in inventory counting functions.
- RF EAS does not work as well as AM and EM on liquids and metals.
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Cited Source: Retail Crime, Security, and Loss Prevention: An Encyclopedic Reference. Charles A. Sennewald, John H. Christman. Copyright 2008, Elsevier Inc.