I Have a cuestion?

I have seen a hand held divice that jam the barcode and the metal ting inside the product... y was wondering how is this posible? what was the funtion that jam the ati-theft ? im new at electronics. Can some one explain please :?:

Thanks . 8)

War
Your posts are starting to go places the Homeland Security Department would be interested in. Best to drop it and move on.
But if you really want some privacy, Install some thick curtains on your windows and back it with metal foil. You can then take any left over foil and make a hat to keep your neighbors electronics from reading your brain waves too.
Dialtone