Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!ukma!wuarchive!uunet!timbuk!willow23!rice
From: rice@willow23.cray.com (Jonathan Rice)
Newsgroups: sci.electronics
Subject: Re: Library anti-theft walk-thru device...????
Message-ID: <100921.10755@timbuk.cray.com>
Date: 9 May 91 17:03:20 GMT
References: <050691.224256WDBURNS%MTUS5.BITNET> <19934@slice.ooc.uva.nl>
Distribution: usa
Organization: Cray Research, Inc., Eagan, MN
Lines: 23

In article <19934@slice.ooc.uva.nl> ropg@ooc.uva.nl (Rop Gonggrijp) writes:
>They mostly work as follows:
>In the book is a strip of metal (any metal) covered by a piece of ferrite.
>The ferrite is magnetised, thus changing the frequency at which this gizmo
>resonates (it is covered in plastic, so it does resonate).
> [much more fascinating electroinformation deleted...]

I can give you an example of how one particular system worked.  The St. Paul
public library, 4th St. branch (the main one), had the usual detector pylons
by the exit door, with the familiar warning notices.  And there were gizmos,
to borrow Mr. Gonggrijp's technical term, in the books.

Apparently, though, the checker-outers of books found that it slowed them
down too much to have to quell the gizmos, so the entire system was turned
off for more than a year.  The theft prevention device was nothing more than
the expectation created by the signs and detectors.

Good old psychology.  Of course, when this was divulged, nobody was willing
to say how well it had worked.  I've no idea if they ever turned it back on
again.

-- 
Jonathan C. Rice  |  Internet: rice@cray.com  |  UUCP: uunet!cray!rice