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
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.
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