At present, there are three kinds of systems widely used in retail industry, namely, radio frequency system, acoustomagnetic system and electromagnetic wave system;
Radio frequency system (RF system):
Radio frequency system (RF) uses radio as transmitting and receiving signal, and the detection frequency range is 7.7 ~ 8.5 MHz. The biggest advantage of radio system is low cost and convenient installation. However, because its anti-theft tag is a circular coil, the system is easily disturbed by some items, such as electronic products such as cash registers and metal objects. , resulting in false positives or false negatives. (However, with the maturity of technology, especially the addition of DSP digital signal processing chips, some anti-interference capabilities have been enhanced. )
At present, it is widely used to protect department stores, clothing stores, supermarkets, luggage and optical shops.
Its working principle is: the transmitter emits a frequency modulation signal of 7.7~8.5MHz to generate an alarm electric field, and when the induction tag enters the electric field, it generates a resonance alarm.
Acoustical magnetic system;
The tuning fork will only cause * * * vibration if the oscillation frequency is the same. Acousto-magnetic system (acousto-magnetic) has realized almost zero false alarm operation by applying this physical principle, and its central frequency is 58kHz. When the acousto-magnetic system tag fixed on the commodity enters the detection area of the system, it will generate * * * vibration, but it will give an alarm only after the receiver receives the * * * vibration signal for four consecutive times (once every 1/50 seconds).
Acousto-magnetic system is characterized by high detection rate of theft, almost zero false alarm, good anti-interference, protection exit width up to 4.0 meters, less affected by metal shielding, and there are two kinds of soft labels and hard labels. The export protection mode of acoustomagnetic system can be channel, concealed or single shot and single receipt, which can be widely used in department stores, supermarkets, clothing, video stores, pharmacies, cosmetics and eye stores.
Electromagnetic wave system:
Electromagnetic systems use electromagnetic waves as detection signals; Its basic principle is to distinguish whether the protected object has a magnetic stripe by detecting the magnetic change of the magnetic stripe by alternating magnetic field, so as to achieve the purpose of anti-theft. Its principle technology is electromagnetic identification technology.
The transmitting end and the receiving end form one or more channels to form a closed-loop magnetic field. When the detected object (such as books and commodities) passes through the channel, the magnetic stripe tag arranged inside generates vibration with the same frequency in the closed-loop magnetic field formed by the channel, and at the same time, it also generates a higher harmonic with a fixed frequency (usually several times the frequency of the magnetic field), commonly known as magnetic stripe signal.
The magnetic stripe signal will produce an alarm response after being processed by the receiving line, while the usual interference signal will be attenuated after being shielded by the internal line, so there will be no response.
The receiving line is set to dual-frequency reception, one for receiving magnetic stripe signals and the other for receiving strong interference signals that cannot be shielded by internal lines. Because interference signals usually appear in the form of short-time pulses (from a few seconds to more than ten seconds), the line automatically turns off the receiving line when it receives such interference signals, and automatically turns on after the interference has passed, restoring the normal start-up state. (Improve anti-interference performance).
The tag of electromagnetic wave system is the smallest, and the tag price is cheap. It can be demagnetized repeatedly, but it is easy to be affected by magnetic or metallic substances and produce false positives. The width of the protective exit is generally about 0.75 meters. The system will not affect magnetic objects (such as audio tapes, video tapes and magnetic cards).
Reasons for using anti-theft system:
1. More and more self-service supermarkets and warehouse-type retail malls bring convenience to customers, but at the same time, the loss of goods is becoming more and more serious.
2. Traditional "civil air defense" technologies, such as man-to-man marking and monitoring, fail to play an effective anti-theft role in time when the store is large and there are many people. At the same time, in order to reduce the loss, we have to prevent it by increasing the number of people, but the cost of shopping malls has also increased.
3. The traditional "civil air defense" technology gives customers a sense of being monitored. It has not really created a leisurely and free shopping environment, but the transformation of "physical defense and technical defense" has not only played an accurate and effective anti-theft effect, but also reduced the number of employees being monitored and created a good shopping environment for customers.
This article is provided by Guangzhou Baole Electronics.