THE anti-theft systems to combat theft of goods hidden under sweatshirts or in bags and backpacks we are all aware of them, given that they are at the entrance to every shop and supermarket. But how many times have you asked yourself how they work Exactly? Why do they ring for some goods and not others?
How anti-shoplifting systems work and how many exist
Anti-shoplifting systems are devices that protect goods from theft. When they pass through the barriers positioned at the exit of the shop or supermarket, the communication between the system and the barriers triggers an audible alarm that immediately warns of the attempted theft. There are various anti-shoplifting systems, but the most used are radio frequency and magneto-acoustic.
In the radio frequency systems Rigid plates or adhesive labels are applied to the goods. It is important to say that these devices can be deactivated at the checkout with the help of mechanical or acousto-magnetic detachers and then they can be remagnetized and reused.
In case of theftthe antennas at the entrances to the shops excite the resonant circuit (consisting of an inductor and a capacitor) inside these devices, and capture the radio signal emitted at a certain frequency.
In the systems magneto-acousticrigid plates (aesthetically the same as those for radio frequency systems) or “thick” adhesive labels are applied to the products with a fake barcode on it.
How an anti-shoplifting system works
At the basis of the operation is the physical principle of “magnetostriction”, linked to the magnetization of the metal bodies (internal to these devices) that undergo it.
The acoustic signal (an alarm, a beep or a siren) is produced by the micro-vibrations of two metal blades activated by magnetic field located on the barriers placed at the entrance – exit of the commercial establishment. This is a very useful and effective system because it allows you to immediately identify the item you are trying to steal, given that thesound alarm comes right from the label itself.
In fact, the label is made up of two small sheets of metal alloy (highly permeable) separated and enclosed by two plastic casings. The distribution of the elements of this alloy gives a high deformation to the plates if they are stressed by the electromagnetic field generated by the barriers at the entrance to the shops, thus the alarm goes off.
Among the most used labels are those with RFID technology (Radio-Frequency Identification). We are talking about a label (it can be made of paper, PVC, polypropylene, etc.) on which there is a small chip which contains within it the information regarding that specific product.
The barriers to entry instead they are gods electromagnetic systems capable of detecting devices that have magnetic material inside them (they must be demagnetized to be able to reuse them).
Sometimes these devices are not seen, because they are “embedded“, i.e. incorporated, but this does not mean that they are not in the product. A product may appear to have no alarms but contain an RFID tag with a microchip inside, and the anti-shoplifting systems at the entrance detect them.
Why do anti-shoplifting systems sometimes ring for no reason?
These systems generally only work when anti-shoplifting devices have been placed on the goods.
However, there are times when, even though no theft has occurred, the barriers set off the alarm. This could happen for example with new shoes or wallets, in which themagnetic labeland which is then removed. Usually the fault can be attributed to a RFID anti-theft that emits signals or responds to specific radio frequencies or magnetic fields and which may trigger an alarm.
