Eli5: how do anti theft radio frequency tags know i bought an item

Question

for context i just bought 3 bags of beef jerky from 5 below and they all had one of those square tags with the lines on them and i only scanned one 3 times at the self checkout how do they get deactivated

Edit [https://imgur.com/a/c3DFJFg](https://imgur.com/a/c3DFJFg) here’s a picture of it

In: Other

Answer 1

At each register and self-check out is a polarizing magnet to disable them triggering the sensor. Used to work there.