How do supermarket sensors work?


I just saw a guy shove loads of chocolate bars and candy into a big black bag, get two beers. I got curious cause usually people don’t put stuff they intend to buy into bags.

Then he proceeds to checkout but only pays for the beers, not a single beep from the sensors. Are they only meant to detect certain items or did the homeless guy have something to disrupt the sensors?

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Unless they’re using RFID technology, most supermarkets rely on optical bar code scanners.

When the candy was in an opaque bag the scanner couldn’t see the barcode.

From what I know, certain (usually more expensive) items have RFID chips/tags inside them that will trigger the sensors when left unpaid. So normal food items, like vegetables, can’t be tracked but a pack of batteries might be.

Rfid’s work on radio frequencies. Have a bag with metal threads interwoven, making a Faraday cage, and the detectors should be bypassed.

Are you sure he didn’t scan them before putting them into the bag?

At my grocery store, [you get a scanner gun when you walk in]( There’s a little holster for it on your cart.

You pick a can of soup off the shelf, scan it, toss it in the cart.

Then at the end you just put the scanner gun into a holster at the self-checkout, and it knows what you bought, and you put your credit card in to pay, and you walk out.

You don’t have to take everything out of your cart to be scanned.

Sensors only sense the presence of specific anti theft devices;

the ones you usually notice are [these](, but there are also more incospicuous ones like [these](×1280/products/220/828/dpm-tapes-4×4-nr.2-rotoli-da-1000-etichette-antitaccheggio-rf-8.2-mhz-falso-barcode__30902.1659096317.jpg?c=1) and [these]( that can be sticked on or even manifactured into some packaged items.

Unlike say a clothing store, a supermarked does’t usually tag all their items, but only the ones that are statistically more likely to be stolen, usually things that are both small and expensive, and dont’t bother with the rest of the merchandise, relying on the fact that people don’t know wich items are tagged or not or outright don’t know how anti theft works.