🚀 go-pugleaf

In article <2634@phri.UUCP> roy@phri.UUCP (Roy Smith) writes:
>	This is also, BTW, one of the ways those stolen-item detectors in
>stores work.  The big plastic clips contain some sort of passive tuned
>circuit, with a diode detector.  The gizmos on either side of the door emit
>RF at some frequency (presumably up in the several hundred Mhz range) and
>listen for harmonics comming back.  The important features of this system
>are that the replicated parts (the big plastic clips) 1) are cheap to
>produce, 2) require no internal power, 3) are not likely to break, and 4)
>can be made physically small.  The latter three are properties which also
>makes this a nice spy technology.

I always wanted to know that.  I've seen thing with a similar purpose at
bookstores.  They looked like strips of aluminized mylar/tinsel, a few inches
ling and about 7mm wide.  They can be `turned off' (so they don't register to
the thing at the exit) by a demagnetizer-like gizmo.

Anybody know how these work?

(Funny thing: one store I know has one of these, but they always leave it
turned off!  Kinda ruins the effect if the power lights and switch are
visible, don't it?)
--
	-Colin Plumb (watmath!watnot!ccplumb)

Silly quote:
That's a horse of a different feather.