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Anti-Theft Devices

  • Thread starter Abstract Dissonance
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A

Abstract Dissonance

Jan 1, 1970
0
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
 
T

Tim Williams

Jan 1, 1970
0
Abstract Dissonance said:
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?

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
 
A

Abstract Dissonance

Jan 1, 1970
0
Tim Williams said:
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

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

Thanks,
Jon
 
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