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What is an acoustic magnetic system?

The acoustic magnetic system uses the resonance phenomenon generated by the tuning fork principle to realize almost zero false alarm operation. When the frequency of the transmitted signal (alternating magnetic field) is consistent with the oscillation frequency of the acoustic magnetic label, the acoustic magnetic label is similar to the tuning fork, which will cause resonance and produce a resonance signal (alternating magnetic field); When the receiver detects 4-8 consecutive (adjustable) resonance signals (once every 1 / 50 second), the receiving system will send an alarm. The AM system is characterized by high anti-theft detection rate, almost zero false alarm, no shielding by metal tin foil, good anti-interference and wide protected outlet (the maximum width of a single system can be protected is 4m).

acoustic magnetic system

Principle of acoustic magnetic system

The transmitter of the detection system emits 58khz low-frequency magnetic wave intermittently in 1 / 75 second to form a detection area around. When the label composed of two special amorphous metal sheets enters the detection area, due to interference or other forms of induction to the electromagnetic field, i.e. resonance signal, this signal will be received by the supporting receiver, resulting in system alarm.

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The acoustic magnetic anti-theft system consists of three parts: one is the detector. It includes transmitter and receiver. The basic principle is to use the transmitting antenna to transmit an alternating magnetic field, form an induction area between the transmitting antenna and the receiving antenna, and use the resonance principle of electromagnetic wave to search whether there is a valid tag within a specific range (i.e. there is a tag not decoded by the decoder). When there is a valid tag, an alarm will be triggered. The second is acoustic magnetic label. It is accurately cut into 58khz size by disorderly arranged amorphous metals, resonates with the magnetic polarizer through entering the detection area and reflects to the receiving support. The third is the decoder, which is a non-contact device with soft label decoding failure. When the cashier checks in, the electronic tag can be decoded without touching the degaussing area; Or a device integrating decoder and laser bar code scanner to complete commodity collection and decoding at one time.
Principle of acoustic magnetic identification acoustic magnetic anti-theft system belongs to single bit radio frequency identification system. The modulation mode adopted is the digital modulation method of amplitude keying (ask). The alternating magnetic field emitted by antenna is modulated by binary encoding signals. It is composed of 0 and 1 single bit sequences of two states. The pulse duration is 20ms, and the pulse duration is about 0. The carrier signal is 58khz (or 60KHZ, 68KHz) low-frequency sinusoidal signal; The modulated signal is an ask signal with an amplitude modulation coefficient of 100%. When the acoustic magnetic tag enters the alternating magnetic field (detection area) excited by ask and the resonant frequency of the tag is consistent with the carrier frequency, resonance will occur in the tag due to magnetostriction effect. When the excited alternating magnetic field is turned off, according to the piezomagnetic effect of the label, the resonance signal will maintain for a period of time and appear damped oscillation; In addition, because mechanical energy and magnetic energy are alternately converted, resonance signal is an acoustic magnetic composite signal, which is the meaning of AM system. Resonance signal is not only the spatial extension of excitation magnetic field, but also has the characteristics of ultrasonic. Therefore, the induction coil in the receiver can easily detect the resonance signal, so as to drive the alarm device of the system. The principle of alternating magnetic field acoustic magnetic identification of acoustic magnetic label: first, the center frequency of the signal is 58khz, and the bandwidth is 57.8khz to 58.2khz (0.4khz), which is the narrowest of all electronic anti-theft systems at present, so it is very unlikely to be disturbed and cause false alarm. The second is the process of the system determining the tag signal. When the transmitting signal is turned off, the receiver receives six (adjustable) resonance signals continuously. If the power and frequency of each resonance signal are the same, it is recognized as a tag signal; If it is an external interference signal, it is impossible to generate 6 identical signals in one second; By repeating the above identification process, the tag signal can be accurately determined and the operation of almost zero false alarm can be realized.

Application of acoustic magnetic system

The acoustic magnetic system has two kinds of anti-theft labels, AM soft label and AM hard tag. There are two series of acoustic magnetic soft labels: Dr and El labels. The former consists of two vibrating plates and one substrate, and the latter consists of one vibrating plate and one substrate. It is suitable for clothing, shoes and hats, bags and daily necessities / food with packaging.
Dr anti-theft label is a non reusable anti-theft label, which loses its function after degaussing. It is mainly pasted on small and easy to steal goods in shopping malls. Special acoustic magnetic anti-theft label degausser and degaussing plate shall be used for degaussing. Do not stick the soft label on the place where the commodity is printed with important instructions, such as commodity composition, use method, warning statement, size and bar code, production date, etc.
The standard AM system has high detection rate and excellent performance close to zero false alarm; Digital technology and software driven intelligent technology; The system is integrated with the support, with a 1.4m protection outlet; Audible and visual alarm. Degaussing equipment can be divided into contact type and non-contact type. The contact type requires the acoustic magnetic label to be in contact with the surface of the degausser, while the non-contact type can degausse the label 12-20cm away from the acoustic magnetic label.
China AM system manufacturer www.tractility.com offers acoustic magnetic anti-theft system.

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