First of all, before understanding how do security tags works, you need to understand the parts of EAS anti-theft.
① EAS anti-theft label: divided into anti-theft hard label and soft label, the anti-theft label is fixed on the product. EAS anti-theft tag is equivalent to a detection signal.
② Degaussing device/unlocking device: The degaussing device is to remove the magnetism of the soft label, and the unlocking device is to unlock the hard label on the product. The ultimate purpose is to make the detection signal attached to the product disappear.
③ EAS anti-theft device: anti-theft device is the most critical part of the EAS system, usually composed of a transmitter and a receiver. Equivalent to a detector, it is usually placed at the exit of the shopping mall to monitor whether there is a product with a label passing through.

Taking the AM sound and magnetic anti-theft system as an example, it uses the physical principle that the tuning fork will cause resonance only when the oscillation frequency is the same to carry out anti-theft. When the anti-theft tag fixed on the commodity enters the detection area of the system, it will match the detection signal. When resonance occurs, the resonance signal will be amplified by the system and converted into an electrical signal to turn on the speaker, which is to trigger an alarm. The beep, beep, beep sound we usually hear is generated in this way!

Therefore, the store chooses different types of labels according to the different characteristics of the products, and attaches the applicable labels to the products. When the customer settles, the cashier will degauss the soft label of the settled product or remove the anti-theft buckle. Since the LC resonant circuit in the label is destroyed, when the product passes through the anti-theft device, it will not resonate with the anti-theft device, and the customer can pass the anti-theft device safely; on the contrary, if the customer holds the product that has not been degaussed by the soft label or has not been demagnetized If the product with the anti-theft buckle is removed, the alarm will be triggered when it passes through the anti-theft device, reminding the store staff to deal with it in time.