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Electronic article surveillance security system

Views:7     Author:Site Editor     Publish Time: 2018-07-05      Origin:Site

Electronic article surveillance security system


Electronic goods anti-theft system abbreviation: "EAS", also known as electronic goods anti-theft system, is one of the commodity security measures widely used in the retail industry. EAS was introduced in the United States in the mid-1960s. It was originally used in the apparel industry. Now it has expanded to more than 80 countries and regions around the world, and its application fields have expanded to various industries such as department stores, supermarkets, books, amusement parks, especially in supermarkets. The application of clothing chain stores has been fully developed.


1. Introduction to EAS

2, EAS classification

3, performance indicators

4, label classification

    ▪ Single bit label

    ▪ Multi-bit label

5, EAS trend

The EAS system is mainly composed of a detector (detection system), a decoder (degausser) and an electronic tag. Electronic tags are classified into soft tags and hard tags. Soft tags are cheaper and adhere directly to the product. Soft tags are not reusable; hard tags are more expensive than soft tags, but can be reused. Hard tags must be equipped with a special nail remover for recycling, and are often used for soft, easy-to-penetrate items. The decoder (degaussing device) is mostly a non-contact device with a certain decoding (degaussing) height. When the cashier accepts the cash or the bag, the electronic tag can be decoded without touching the degaussing area. There is also a device that combines the decoder and the laser bar code scanner, so that the goods collection and decoding can be completed in one time, which is convenient for the cashier's work. In this way, it must cooperate with the laser bar code supplier to exclude the two. Mutual interference to improve decoding sensitivity. The detector is typically a detection system device at the mall entrance or exit or cashier channel. After receiving the correct payment from a customer for the purchase of a product, the cashier can authorize the item and legally leave a designated area by degaussing and decoding the label affixed to the item. Undecoded goods are taken away from the mall, and when passing through the detector device, an alarm is triggered to alert the cashier, the customer, and the store security personnel to deal with it in a timely manner.

EAS classification

The EAS system is developing rapidly and can be divided into single-bit systems and multi-bit systems.

A multi-bit system is currently represented by a radio frequency identification system (RFID system). Radio frequency identification (RFID) is a term used to describe any device that can be sensed by radio frequency. It usually refers to the use of radio frequency. To read the information on a small device called a tag. The RFID system consists of a tag, a reader and an antenna. The working principle is as follows: after the tag enters the magnetic field, it receives the RF signal emitted by the reader, and sends the product information (passive tag, passive tag or passive tag) stored in the chip by the energy obtained by the induced current, or actively sends a certain A frequency signal (Active Tag, active tag or active tag); the reader reads the information and decodes it, and sends it to the central information system for data processing. RFID tags allow us to use radio waves to read and read multiple tags in batches, far more than barcodes. In addition to the anti-theft function, the same mark can also be used to prove the attribution of the item, provide the anti-theft function of the electronic product that the EAS system can realize, and use the RFID to better achieve the purpose.

With the unification of RFID standards, RFID tags have been widely recognized and applied, breakthroughs in recognition rate and stability technology bottlenecks, and the realization of low-cost tags, RFID will replace EAS to dominate the market for electronic goods anti-theft.

The single-bit identification system is applied in the main technology of the EAS system and can be divided into acoustic magnetic system, radio frequency system and electromagnetic wave system.

Since the single-substance system has only two states, it can only report the presence or absence of an item, and has no ability to report other details such as what the item is. EAS systems of different technologies have great differences in product price, reading distance and reliability. Magnetic strips used in electromagnetic wave systems and RF tags used in RF systems are relatively inexpensive; acoustic magnetic tags are more expensive. Both have a soft label (a one-time label that is permanently attached to the item) and a hard label (a reusable anti-theft label that can be recycled).

Acoustic magnetic system, the so-called Acoustic Magnetic (AM), is a resonance phenomenon generated by the tuning fork principle, which realizes almost zero false alarm operation. The principle is shown in Figure 1. When the frequency of the transmitted signal (alternating magnetic field) coincides with the oscillation frequency of the acoustic magnetic label, the acoustic magnetic label is similar to the tuning fork, causing resonance, generating a resonance signal (alternating magnetic field); when the receiver detects 4-8 times in succession (adjustable) After the resonance signal (once every 1/50th of a second), the receiving system will give an alarm. The characteristics of the acousto-magnetic system are high anti-theft detection rate, almost zero false alarm, shielding from metal foil, good anti-interference, and wide exit protection (single system can protect 4 meters wide).

The radio frequency system (Radio Frequency, RF) uses radio waves as the signal for transmitting and receiving. The detection frequency ranges from 6 to 10 MHz, and the international common frequency is 8.2 MHz. The biggest advantage of the radio system is that the system cost is very low and the installation is convenient. However, because the anti-theft tag is a toroidal coil type and the frequency is relatively high, the system is susceptible to interference from some items, such as electronic products such as cash registers, spotlights, coiled cables, and metal objects, which may interfere with it. , causing system false positives or not reporting.

The Electromagnetic System (ES) uses electromagnetic waves as detection signals. The electromagnetic wave system has a small label, and the label price is also cheap, and the demagnetization can be repeated, but it is susceptible to false alarms due to the influence of magnetic or metallic substances. Although it is produced almost at the same time as the radio frequency system, the price and technical reasons determine its low acceptance in the market. Due to its label characteristics and price advantage, it is currently used in the domestic book market.


How to choose EAS system? How does the supermarket anti-theft system judge good or bad? How to judge the quality of the clothing anti-theft system?

The above three questions are actually a problem. How to choose the right EAS system?

Each user has the characteristics of its choice of anti-theft system, generally considering product quality, product price, after-sales service and other aspects. If it is more sensitive to price, it can only choose cheap RF anti-theft system and low-cost imitation sound and magnetic system. There are many kinds of such products, which are not good enough, and the quality and after-sales are difficult to guarantee. If it is not sensitive to the price, you can choose the manufacturer of the brand anti-theft system, such as the US News. Of course, if you want cheaper and better quality and after-sales service, you can choose some domestic companies with good reputation, long-term service, and guaranteed services, such as Nanjing Bohang Electronics. The following is a technical analysis of the characteristics of each system.

First of all, from the perspective of product quality: evaluation of EAS system performance indicators have system detection rate, system false positives, environmental interference resistance, metal shielding, protection width, protection of product types, anti-theft tag performance / size, degaussing equipment.

Detection rate

The detection rate refers to the number of alarms when a valid number of units of a valid label passes through different positions of the detection area in different directions.

Since the label of the product anti-theft system has directionality, the concept of the detection rate should be based on the average of the detection rates in all directions. In terms of the three most commonly used principles on the market, the acoustic magnetic anti-theft system has the highest detection rate, generally exceeding 95%; the radio/RF system detection rate is between 75-95%; the electromagnetic wave detection rate is generally 50- Between 70%. A system with a low detection rate is likely to have a false negative rate when a product is taken out, so the detection rate is one of the main performance indicators for evaluating the quality of the anti-theft system. Of course, the detection rate is based on the better system quality. The detection rate of different product anti-theft system manufacturers will be very different, and the installation spacing will also affect the detection rate.

2. System false positives

System false alarm refers to the alarm of the non-theft tag trigger system. If a non-label item triggers an alarm, it will bring difficulties to the judgment of the staff member and even cause conflicts between the customer and the shopping mall. Due to the limitation of the principle, the current common EAS system can not completely eliminate the false positives, but the performance will be different. The key to selecting the system is to look at the false positive rate.

3. Resistance to environmental interference

When the device is disturbed (mainly the interference between the power supply and the surrounding noise), the system will send an alarm signal when no one passes or does not trigger any alarm items. This phenomenon is called false report or self-sounding.

Radio/RF systems are often subject to self-sounding phenomena due to environmental disturbances. Therefore, some systems have an infrared device installed, which is equivalent to the installation of an electric switch. Only when the personnel pass through the system and blocks the infrared rays, the system starts to work. When the person passes, the system is in standby state. Although this solves the self-sounding when no one passes, it still cannot solve the self-sounding situation when someone passes by.

Electromagnetic wave systems are also susceptible to environmental disturbances, especially magnetic media and power supply disturbances that affect system performance.

Due to the unique resonance of the acousto-magnetic system and the intelligent technology, the system is controlled by the microcomputer and software, and the surrounding environment noise is automatically detected, so it can adapt to the environment well and has better resistance to environmental interference.

4. The degree of shielding by metal objects

Many goods in shopping malls and supermarkets carry metal objects, such as food wrapped in metal foil paper, cigarettes, cosmetics, medicines, etc.; as well as products that have their own metal, such as batteries, CD/VCD discs, hairdressing supplies, hardware tools. Etc.; other shopping carts, shopping baskets, etc. The influence of metal-containing articles on the EAS system is mainly the shielding effect on the inductive label, so that the system detecting device can not detect the existence of an effective label or the detection sensitivity is greatly reduced, and the system does not issue an alarm.

The most severely affected by metal shielding is the radio/RF RF system, which may be one of the main limitations of radio/RF performance in actual use. The electromagnetic wave system will also be affected by metal objects. When a large piece of metal enters the detection area of the electromagnetic wave system, the system will “stop”. When the metal shopping cart and the shopping basket pass, the goods inside will have a valid label. No alarm is generated because of shielding. In addition to affecting pure iron products such as iron pans, the sound magnetic system will be affected by other metal items such as metal objects/tin foil paper, metal shopping carts/shopping baskets, etc.

5. Protection width

Shopping malls need to consider the protection width of the anti-theft system, so as to avoid the width between the supports is too narrow, affecting customers in and out. Moreover, the malls hope that the entrances and exits are more spacious.

6. Protection of product types

The goods in the supermarket can generally be divided into two categories. One type is “soft” goods, such as clothing, shoes and hats, and knitwear. These types are generally protected by hard labels and can be reused. The other type is “hard” goods, such as cosmetics, food, shampoo, etc., which are soft. Label protection, degaussing at the checkout counter, usually one-time use.

7. Anti-theft tag performance

The anti-theft tag is an important part of the entire electronic anti-theft system. The performance of the anti-theft tag affects the performance of the entire anti-theft system. Some labels are susceptible to moisture; some cannot be bent; some labels can be easily concealed in the box of the product; some will cover useful instructions on the product and so on.

8. Degaussing equipment

The reliability and ease of operation of degaussing equipment are also important factors in the selection of anti-theft systems. At present, the more advanced degaussing devices are non-contact type, which generates a degaussing area of a certain height. When the effective label passes, the degaussing of the label is instantaneously completed, and there is no need to contact the degaussing device, which facilitates the cashier operation and speeds up the cash register.

9. Single bit label

Tags that remain on the item and are neutralized by the salesperson are considered to be deactivated. One type of deactivated tag is an electronic circuit consisting of an inductive component and a capacitive component that resonates at a certain radio frequency.

The magnetic label consists of a magnetic strip of soft magnetic material. Such a magnetic tag can be magnetized or demagnetized by interacting with a ferromagnetic element made of a hard magnetic material. Under the action of a magnetic field with a certain frequency, the soft magnetic strip will resonate and generate harmonics. This allows identification of the tag. The hard ferromagnetic element is magnetized or demagnetized, which also causes the tag to be activated or deactivated.

The acousto-magnetic label is composed of a strip of magnetostrictive material and a strip of high-coercive magnetic material. A magnetic field with a specific frequency will cause the coercive magnetic strip to resonate. This resonance can be detected by a receiver sensitive to the magnetic field generated by the mechanical resonant magnetostrictive material. Deactivation of the tag can be achieved by changing the magnetic bias of the magnetic strip.

For radio frequency identification (RFID) technology, EAS is just a simple additional feature. Compared with other traditional ESAs, RFID EAS has the following advantages: it not only can notify the existence of an item by triggering an alarm system, but also can advertise what the item is; it can be ordered by the same label system from the manufacturer of the goods. All sites on the retailer's entire distribution channel simultaneously turn off or turn on EAS; the tags can be easily controlled by the tag's read-write protocol, instead of using a bulky magnetic block to get information from some retailers like now. Remove all sorts of messy credit cards.

When the system uses wireless communication, the label can be packaged in the merchandise, thus avoiding leaving the package with the traditional label behind the store when the merchandise is removed from the package. The EAS function can be integrated with the identification system and the tracking system without additional cost.

10. Multi-bit tags

A traditional EAS tag is a single-bit device and cannot be switched between on and off by a programming signal.

The resonant circuit is obtained by selecting the appropriate values of the resistor R, the capacitor C, and the inductor L in the circuit, so that the reactance of the circuit is minimized at the resonance frequency.

One such method is to place the resonant circuit on a thin insulating dielectric substrate to form a label that can be used with an EAS system. Typically, the resonant circuit coil consists of a closed loop of conductive elements with specific impedance and inductance values. The capacitive element in the closed loop is composed of two thin metal conductive films respectively placed on opposite surfaces of the insulating dielectric substrate. This is to stick the label on the item and it can prevent theft. The radio frequency of the radio frequency signal transmitted from the base station is at or near the resonant frequency of the resonant circuit. Once the tag enters the RF signal field, the absorption of the RF signal by the tag will cause a change in the oscillating current in the base station resonant circuit and cause the power in the receiving coil to drop. These two effects can be used to detect the presence of the tag, which in turn detects the item to which the tag is attached. So once the above two are detected by the pickup coil.

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