Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!zaphod.mps.ohio-state.edu!pacific.mps.ohio-state.edu!linac!tellab5!laidbak!obdient!vpnet!cgordon
From: cgordon@vpnet.chi.il.us (Gordon Hlavenka)
Newsgroups: sci.electronics
Subject: Stock control tags
Message-ID: <271618ef-4a7.1sci.electronics-1@vpnet.chi.il.us>
Date: 12 Oct 90 21:55:03 GMT
References: <1990Oct12.044801.8842@csis.dit.csiro.au>
Lines: 30


I don't know how all of them work, but...

Some reflect/absorb RF with a unique signature.  A detector then radiates
some spread of RF, and looks for the signature.  This tag is deactivated by
removing it from the goods.

The "magnetic" ones, I think, are probably decoys.  The whole system is to
make you _think_ there's something going on, but even the clerks wouldn't
know the truth.  This may be wrong in many cases, but it _is_ true in some.

There might be a second layer which is fused by _pressure_, thereby
deactivating an RF-signature device by shorting it out.  This would be
dragged across a roller, but wouldn't involve magnetism.

One system I know of is used in books.  A strip about 1/8" wide by 2 or 3
inches long is inserted into the binding of the book.  The strips themselves
are pretty expensive, so stores that use them only protect some books.  I
don't know how these are turned off.

I knew a guy a few years back who collected these tags.  He'd secrete the
active portions in his wallet, pockets, etc.  And he'd set off alarms all
the time.  This was his idea of fun -- personally I stayed away from him in
malls.  He'd make up stories about having a plate in his head or somesuch,
and explain this to security people.  A couple of stores tried to ban him on
principle, but I don't know if anything ever came of it.

-----------------------------------------------------
Gordon S. Hlavenka            cgordon@vpnet.chi.il.us
Disclaimer:                Yeah, I said it.  So what?