Electronic article surveillance
Electronic article surveillance is a type of system used to prevent shoplifting from retail stores, pilferage of books from libraries, or unwanted removal of properties from office buildings. EAS systems typically consist of two components: EAS antennas and EAS tags or labels. EAS tags are attached to merchandise; these tags can only be removed or deactivated by employees when the item is properly purchased or checked out. If merchandise bearing an active tag passes by an antenna installed at an entrance/exit, an alarm sounds alerting staff that merchandise is leaving the store unauthorized. Some stores also have antennas at entrances to restrooms to deter shoppers from taking unpaid-for merchandise into the restroom where they could remove the tags.
History
EAS tags that could be attached to items in stores were invented by Arthur Minasy in 1964. He filed a patent for his "Method and Apparatus for Detecting the Unauthorized Movement of Articles" in 1965 with the patent being granted in 1970.Types
There are several major types of electronic article surveillance technologies, each designed to detect unauthorized removal of merchandise or materials using different electromagnetic or acoustic principles:- Electromagnetic – Also known as magneto-harmonic or based on the Barkhausen effect, this system uses amorphous metal strips that respond to low-frequency magnetic fields. EM EAS is particularly suited for libraries, pharmacies, and applications involving small or metallic items.
- Acousto-Magnetic – Also known as magnetostrictive, this system uses vibrating metal strips that resonate at a specific frequency when exposed to an AM signal. AM is widely used in retail stores, especially for items requiring high detection reliability.
- Radio Frequency – Typically operating at 8.2 MHz, RF systems detect resonant circuits within tags. RF EAS is commonly used in clothing stores, supermarkets, and environments with fewer metallic or liquid interferences.
- Microwave EAS – Less common today, these systems use microwave energy combined with RF fields to detect tagged items. They are generally more expensive and were mostly deployed in niche applications.
- Video Surveillance Integration – While not a form of EAS per se, closed-circuit television systems are often integrated with EAS solutions for enhanced security and incident verification.
- Concealed EAS Systems – These are built into floors, door frames, or shelving, allowing discreet tag detection without visible antennas. They are used in high-end retail and aesthetic-sensitive environments.
Concealed EAS systems
Electromagnetic systems
Electromagnetic article surveillance tags use a strip of amorphous metal paired with a layer of ferromagnetic material. This design allows repeated activation and deactivation.When exposed to low-frequency alternating magnetic fields, the tag emits harmonic signals due to its nonlinear magnetic behavior. These signals are detected by antennas placed at exits or secure zones.
Magnetizing the ferromagnetic layer biases the amorphous strip into saturation, which suppresses signal generation and deactivates the tag. Demagnetizing it restores detectability. EM EAS systems function reliably on metal surfaces, foil packaging, and small or curved items, in environments where other technologies, such as RF or RFID, may perform less effectively.
Electromagnetic EAS systems are widely used in libraries to secure books with tattle tapes, DVDs, and other media items. These systems support high-frequency reactivation and deactivation cycles, making them ideal for frequent circulation environments. Tattle tapes are thin electromagnetic security strips embedded in or attached to media, triggering alarms if items are removed without proper checkout.
In retail environments, EM EAS tags provide effective protection for a broad range of products, including small, curved, or metallic items such as cosmetics, infant formula cans, pharmaceuticals, DIY tools, and household appliances. EM technology is particularly effective in detecting items concealed within foil-lined bags or metal briefcases, helping to counter sophisticated shoplifting techniques such as booster bag theft.
Document protection is another key application: EM elements can be embedded in Security paper to protect sensitive hardcopy materials such as trade secrets or classified government files. These embedded microwires are detectable by EM gates or metal detectors, and some printers are configured to work only with certified paper.
Acousto-magnetic systems
These are similar to magnetic tags in that they are made of two strips: a strip of magnetostrictive, ferromagnetic amorphous metal and a strip of a magnetically semi-hard metallic strip, which is used as a biasing magnet and to allow deactivation. These strips are not bound together but free to oscillate mechanically.Amorphous metals are used in such systems due to their good magnetoelastic coupling, which implies that they can efficiently convert magnetic energy into mechanical vibrations.
The detectors for such tags emit periodic tonal bursts at about 58 kHz, the same as the resonance frequency of the amorphous strips. This causes the strip to vibrate longitudinally by magnetostriction, and it continues to oscillate after the burst is over. The vibration causes a change in magnetization in the amorphous strip, which induces an AC voltage in the receiver antenna. If this signal meets the required parameters, the alarm is activated.
When the semi-hard magnet is magnetized, the tag is activated. The magnetized strip makes the amorphous strip respond much more strongly to the detectors, because the DC magnetic field given off by the strip offsets the magnetic anisotropy within the amorphous metal. The tag can also be deactivated by demagnetizing the strip, making the response small enough so that it will not be detected by the detectors.
AM tags are three dimensional plastic tags, much thicker than electro-magnetic strips and are thus seldom used for books.
Radio frequency (RF) systems
These tags are essentially an LC tank circuit that has a resonance peak anywhere from 1.75 MHz to 9.5 MHz. The standard frequency for retail use is 8.2 MHz. Sensing is achieved by sweeping around the resonant frequency and detecting the dip.Deactivation for 8.2 MHz label tags is typically achieved using a deactivation pad. In the absence of such a device, labels can be rendered inactive by punching a hole, or by covering the circuit with a metallic label, a "detuner". The deactivation pad functions by partially destroying the capacitor. Though this sounds violent, in reality, both the process and the result are unnoticeable to the naked eye. The deactivator causes a micro short circuit in the label. This is done by submitting the tag to a strong electromagnetic field at the resonant frequency, which induces voltages exceeding the capacitor's breakdown voltage.
In terms of deactivation, radio frequency is the most efficient of the three technologies given that the reliable "remote" deactivation distance can be up to. It also benefits the user in terms of running costs, since the RF de-activator only activates to send a pulse when a circuit is present. Both EM and AM deactivation units are on all the time and consume considerably more electricity. The reliability of "remote" deactivation capability makes for a fast and efficient throughput at the checkout.
Deactivation of RF labels is also dependent on the size of the label and the power of the deactivation pad. It is common to find RF deactivation built into barcode flat and vertical scanners at the POS in food retail especially in Europe and Asia where RF EAS technology has been the standard for nearly a decade. In apparel retail deactivation usually takes the form of flat pads of approx. 30x30 cm.
Microwave systems
These permanent tags are made of a non-linear element coupled to one microwave and one electrostatic antenna. At the exit, one antenna emits a low-frequency field, and another one emits a microwave field. The tag acts as a mixer re-emitting a combination of signals from both fields. This modulated signal triggers the alarm. These tags are permanent and somewhat costly. They are mostly used in clothing stores and have practically been withdrawn from use.Tag pollution
One significant problem from source tagging is something called "tag pollution" caused when non-deactivated tags carried around by customers cause unwanted alarms, decreasing the effectiveness and integrity of the EAS system. The problem is that no store has more than one system. Therefore, if a store actually has an anti-shoplifting system to deactivate a label they will only deactivate the one that is part of their system. If a store does not use an EAS system, they will not deactivate any tags at all. This is often the reason why people trigger an alarm entering a store, which can cause great frustration for both customers and staff.Discussion
Occasional versus professional shoplifters
EAS systems can provide a solid deterrent against casual theft. The occasional shoplifter, not being familiar with these systems and their mode of operation, will either get caught by them, or preferably, will be dissuaded from attempting any theft in the first place.Informed shoplifters are conscious of how tags can be removed or deactivated. A common method of defeating RF tags is the use of so-called booster bags. These are typically large paper bags that have been lined with multiple layers of aluminium foil to effectively shield the RF label from detection, much like a Faraday cage. A similar situation would be the loss of signal that a cell phone suffers inside an elevator: The electro-magnetic, or radio waves are effectively blocked, reducing the ability to send or receive information.
However, they may miss some tags or be unable to remove or deactivate all of them, especially if concealed or integrated tags are used. As a service to retailers, many manufacturers integrate security tags in the packaging of their products, or even inside the product itself, though this is rare and not especially desirable either for the retailer or the manufacturer. The practical totality of EAS labels are discarded with the product packaging. This is of particular application in everyday items that consumers might carry on their person to avoid the inconvenience of potentially live reactivated EAS tags when walking in and out of retail stores.
Hard tags, typically used for clothing or ink tags, known as benefit denial tags, may reduce the rate of tag manipulation. Also, shoplifters deactivating or detaching tags may be spotted by the shop staff.
Shoplifting tools are illegal in many jurisdictions, and can, in any case, serve as evidence against the perpetrators. Hence, informed shoplifters, although they decrease their risk of being caught by the EAS, expose themselves to much greater judicial risks if they get caught with tools, booster bags, or while trying to remove tags, as this shows intent to steal.
The possession of shoplifting tools can lead to the suspect being arrested for suspicion of theft or "Going equipped for stealing, etc." within the UK judicial system.
In summary, while even the least expensive EAS systems will catch most occasional shoplifters, a broader range of measures are still required for an effective response that can protect profits without impeding sales.