The big black things that u walk through at the exits of wal mart, big 5, or hollywood video
2007-04-09 06:16:22 · 3 answers · asked by Nick 1 in Politics & Government ➔ Law & Ethics
the magnetic strips, usually hidden in merchandise, so you can't find them, they have barcodes on them usually
1-3 years minimum though
2007-04-09 06:20:36 · answer #1 · answered by gtamayo1 4 · 0⤊ 0⤋
They detect little plastic tabs with minature radio frequency circuits built-in. There are large electromagnetic coils that radiate RF energy of a certain frequeny, which excites the circuit in the little plastic tabs, and causes it to re-radiate on a slightly different frequency. If this slightly different radio frequency is detected in the detector coils of the big black thing, the alarm goes off.
It's not purely magnetic, nor is it a bar code -- it's electromagnetic.
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2007-04-09 13:22:49 · answer #2 · answered by tlbs101 7 · 1⤊ 0⤋
It detects a piece of metal that is placed inside the package.
LOL...yeah....what tlbs101 said!
2007-04-09 13:19:59 · answer #3 · answered by Wandering 4 · 0⤊ 0⤋