how do the sensory machines at the doors of big shopping chains work? how do they know when someone is walking out of the store without paying for the certain object

Question

how do the sensory machines at the doors of big shopping chains work? how do they know when someone is walking out of the store without paying for the certain object

In: Technology

Answer 1

I may be wrong here but “experience” has taught me that the sensors only work on products that have some sort of device, whether it’s a dye pack or just the little metal strip inside the box somewhere. This probably isn’t much help because I don’t know exactly what relays that signal to the sensors. Even less help, when I was little I thought they were just metal detectors.