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

The little plastic tabs on CD boxes, the barcode style stickers with wires in them, and the big tags on clothing.

They generate an electro magnetic field when you walk through the sensors at the doors. The sensors pick that up and sets the alarm off.

There are many ways to easily defeat them, and further explanation of how they work will allow people to figure those out.