How does a grocery shop alarm know if you paid for something?
- Monday Nov 2,2009 04:33 PM
- By diddy
- In Others
I know clothes etc use RFID chips but how do supermarkets know whether I have paid for milk or a can of beans. I’d really like to know how it’s done as Rfid chips cost 50 cents in bulk so…
50 Cents, Clothes, Grocery Shop, Milk, Rfid Chips, Supermarkets
One Comment
They don’t use RFID chips, they use resonant label tags. Resonant tags cost about 4 cents each. They consist of precisely cut pieces of aluminum foil between two pieces of paper.
In the most typical system, you walk between two vertical antennas and an 8.2 MHz pulse is emitted. If there’s a label on any item you’re carrying, it will "ring" almost the way a glass does if you tap it. The "ring" is detected by the antennas and an alarm is sounded.
The tags are generally only put on higher-priced items. The cashiers need to know which items are tagged to disable the tags.
My link leads to a typical tag used by grocery stores.
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