Eli5: how a scanner at the store can detect when one item hasn’t been scanned (which only has a barcode on it) while dozens of the same item can be leaving at the same time

Question

Eli5: how a scanner at the store can detect when one item hasn’t been scanned (which only has a barcode on it) while dozens of the same item can be leaving at the same time

In: Technology

Answer 1

Weight. Just past the scanner is a scale that weighs the scanned product. Along with the SKU and price the barcode also maps to a product weight. Scan one item but set down three? The weight difference alerts the scanner.