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Anti-Theft Devices

I brought something today and it contained one of those anti-theft things that are like about 1.5inx1/4in or so and has 3 pieces of metal in it. I'm curious to how this works. I don't see any circuitry on it so its not some type of transmission device? I'd guess the its used in some type of resonance(like an antena) but not sure how that would work since I'd assume that the method could mess up electrical equipement and stuff. The very thing metal strips have a slight curvature and are rectangular except for another one that has triangle like endpoints.

Anyone know the specifics about it?

Thanks, Jon

Reply to
Abstract Dissonance
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Y'mean an RFID tag? Those use an RF resonant circuit, you excite it with some RF (beamed between those security checkpoint things in front of the doors) and if it absorbs RF, it's "live". The thing at the checkout blows a fusible link inside, rendering it ineffective at the door, resulting in no absorbance and detection.

More complicated ones can have a chip in them that's powered by the RF, then does something to communicate (switched short on the tank, modulating frequency or amplitude?).

At least I think that's the poop on some of these things, these days.

Small ones of course can be implanted under the skin, as done for some pets for instance (and people!).

Tim

-- Deep Fryer: a very philosophical monk. Website:

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Reply to
Tim Williams

ok... thats basicaly what I thought. I'll probably understand more details if I ever get into RF stuff.

Thanks, Jon

Reply to
Abstract Dissonance

thanks,do u know it's circuits.....

Reply to
nanthuathani

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