How do the non-removable security tags on supermarket products work?



How do the small security tags (usually stuck on with adhesive) work on things in supermarkets, like meats, dvds etc?

They don’t get removed after purchase, so how come that individual item doesn’t set of the alarms even though the tag is still on it?

In: Technology

Stickers and such need to be deactivated at the register. You probably don’t even notice it, but your cashier runs it across a pad or other such scanner and it deactivates. If it hasn’t been deactivated, it’ll set off the alarm.

At checkout the tags are passed over the deactivation system that is usually built into the register scanner. Once that tag is deactivated it won’t alarm when you exit and the tag can’t be reused.

They either get removed when purchased or are simply deactivated, causing them to not respond to the sensors anymore when you are leaving the store. Where I work, we just have a small device that pops the tags off though.

Each tag sends out a radio message when a reader lights it up with radio frequency waves (the reader’s signal also provides the power for the tag). The message is a large number, large enough that it is astronomically unlikely you’ll find two with the same number in the same shop, burned into each tag when it was manufactured.

When the shop gets items with such tags (or sticks them onto stuff), the number of the tag gets entered into the shop’s database. When the cashier pulls the item across their reader, the number gets removed. If a reader in the security gates detects a tag with a number still in the inventory, you get an alarm.

The detectors at the doors send power the tag as it passes through them, when powered the tag emits a signal back to the detectors.

This is called wireless electricity, Nikolas Tesla came up with it, and many others have tried it on small scales. Think about how you can send and receive signals with with a small, low power, wifi emitter. Boost up the power of the emitter and you can power a low power device.