Electronic Article Surveillance

Electronic article surveillance is a technological method for preventing shoplifting from retail stores, pilferage of books from libraries or removal of properties from office buildings. Special tags are fixed to merchandise or books. These tags are removed or deactivated by the clerks when the item is properly bought or checked out. At the exits of the store, a detection system sounds an alarm or otherwise alerts the staff when it senses active tags. Some stores also have detection systems at the entrance to the restrooms that sound an alarm if someone tries to take unpaid merchandise with them into the restroom. For high-value goods that are to be manipulated by the patrons, wired alarm clips called spider wrap may be used instead of tags.

Surveillance tags that could be attached to items in stores were first invented by Arthur Minasy in 1966. Initially the concept of pilferage becoming a real concern to retailers started in 1964 when a requirement was raised by a retailer in Ohio after he faced pilferage in his store. Thereafter lots of research started happening and today it has reached a stage where visible deterrence have moved on to where a retailer does not even have to install pedestals in a store.

Types of Electronic Article Surveillance

There are several major types of electronic article surveillance systems:

• Electro-Magnetic, also known as magneto-harmonic or Barkhausen effect
• Acousto-magnetic, also known as magnetostrictive
• Radio Frequency (8.2 MHz)
• Microwave
• Video surveillance systems (to some extent)
• Concealed EAS Surveillance Systems

1. Electro-magnetic systems

These tags are made of a strip of amorphous metal (metglas) which has a very low magnetic saturation value. Except for permanent tags, this strip is also lined with a strip of ferromagnetic material with a moderate coercive field (magnetic “hardness”). Detection is achieved by sensing harmonics and sum or difference signals generated by the non-linear magnetic response of the material under a mixture of low-frequency (in the 10 Hz to 1000 Hz range) magnetic fields.

When the ferromagnetic material is magnetized, it biases the amorphous metal strip into saturation, where it no longer produces harmonics. Deactivation of these tags is therefore done with magnetization. Activation requires demagnetization.

The EM systems are suitable for libraries to protect books and media. In the retail segment, unlike AM and RF, EM can protect small or round items and products with foil packaging or metal objects, like cosmetics, baby milk cans, medicines, DIY tools, homeware etc. EM systems can also detect objects placed in foil bags or in metal briefcases.

A further application is the Intellectual property (IP) protection against theft: Security paper with embedded microwires, which is used to detect confidential documents if they are removed from a building.

2. 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 (to increase signal strength) 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 (correct frequency, repetition, etc.), 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.

Called Emtag by B&G International, this type of tag is often attached to the inside of a plastic surround permanently attached to the power cords of hand tools and equipment.

3. Radio frequency systems

These tags are essentially an LC tank circuit (L for inductor, C for capacitator) 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 3 technologies (RF, EM, AM – there are no microwave labels) given that the reliable “remote” deactivation distance can be up to 30 cm (11.8 in). 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 (i.e. non-contact or non-proximity deactivation) capability makes for a fast and efficient throughput at the checkout.

Efficiency is an important factor when choosing an overall EAS solution given that time lost attempting to deactivate labels can be an important drag of cashier productivity as well as customer satisfaction if unwanted alarms are caused by tags that have not been effectively deactivated at the point of sale.

Deactivation of RF labels is also dependent on the size of the label and the power of the deactivation pad (the larger the label, the greater the field it generates for deactivation to take place. For this reason very small labels can cause issues for consistent deactivation). 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. 30×30 cm.

4. Microwave systems

These permanent tags are made of a non-linear element (a diode) coupled to one microwave and one electrostatic antenna. At the exit, one antenna emits a low-frequency (about 100 kHz) 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.

5. Video Surveillance

Video surveillance involves the act of observing a scene or scenes and looking for specific behaviors that are improper or that may indicate the emergence or existence of improper behavior.

Common uses of video surveillance include observing the public at the entry to sports events, public transportation (train platforms, airports, etc.), and around the perimeter of secure facilities, especially those that are directly bounded by community spaces.

The video surveillance process includes the identification of areas of concern and the identification of specific cameras or groups of cameras that may be able to view those areas. If it is possible to identify schedules when security trends have occurred or may be likely to occur, that is also helpful to the process. Then, by viewing the selected images at appropriate times, it is possible to determine if improper activity is occurring.

6. Concealed EAS Systems

These new types of systems have caught on lately as there are no visible pedestals or hindrance in the store facade. These systems are installed below the floor and dropped from the ceiling, and can then protect merchandise of retailers from being stolen as the entire range of door is covered. Various studies and researches have been done into making this technology powerful and effective. There are site conditions and other parameters which enable them to be successfully installed but often it has now been noted that malls insist on concealed system as a mandate to increase the shopping experience- for example a part of Dubai Mall in United Arab Emirates do not allow any visible systems. Concealed Systems will be the way to go for the future.