Anti-Theft Devices

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:

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

Thanks, Jon

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