2007-04-09 09:28:32 · 3 answers · asked by Alicia <3 2 in Science & Mathematics ➔ Engineering
Little plastic strips contain minature RF circuits. When you pass through the "gate", the sensors are transmitting an RF wave that resonates in the circuit (in the plastic strip), and energizes it. It then re-radiates a slightly different frequency that the sensors pick up on and sound the alarm.
Bar codes do not set off the alarm, nor are the little plastic thingys strictly magnetic (otherwise any magnetic material would give false alarms).
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2007-04-09 09:48:50 · answer #1 · answered by tlbs101 7 · 0⤊ 0⤋
I think most of them work on the principle of induction. There's a litte coil or loop of metal in most of the tags, and when this passes through the barriers at the door, it sets off the alarm.
2007-04-09 16:32:18 · answer #2 · answered by dudara 4 · 1⤊ 0⤋
why would you wnat to know?
do you steal?
2007-04-09 16:31:41 · answer #3 · answered by panamagurl315 2 · 0⤊ 1⤋