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From: mfb@cci632.UUCP
Newsgroups: sci.electronics
Subject: Re: Stolen item-detectors (Was: Re: Laser eavesdropping)
Message-ID: <1140@cci632.UUCP>
Date: Thu, 23-Apr-87 13:48:16 EST
Article-I.D.: cci632.1140
Posted: Thu Apr 23 13:48:16 1987
Date-Received: Sat, 25-Apr-87 05:45:22 EST
References: <959@obelix.UUCP> <1104@nonvon.UUCP> <5941@pur-ee.UUCP>
Reply-To: mfb@cci632.UUCP (Mark F. Bowen)
Organization: CCI, Communications Systems Division, Rochester, NY
Lines: 30
Keywords: Library books
Summary: Inquiry about library book theft protectors

Sender:

In article <5941@pur-ee.UUCP> wn9nbt@pur-ee.UUCP (Dave Chasey) writes:
>
>                                                    How about the
>ones that are in Library books in some libraries ?

>                    I have been told that the sensor is on the back
>side of the envelope that they attach inside the rear cover that holds
>the checkout card.

I recently checked a book out of the R.I.T. library and I noticed that
there was a piece of gray paper that was rather thick affixed to the inside
of the front cover.  It was easy to peel back one corner of the paper to
discover that it had a foil backing (aluminum or lead, I'm not sure which).
This is the only book that I've ever found with this foil affixed to the
inside of the cover.  Perhaps most books that are sold to libraries have
this foil built-in to the cover.

I recall that one of the people working at the check-out counter said
something about having to "discharge" the book.  On the other hand, I recently
checked out some reading material that was on 24 hour reserve, and the
a check-out person had to hand it to me _around_ the detector, apparently
because they could NOT "discharge" the item.

The items that can be discharged are just rubbed briefly on a metal plate
that sits under the edge of the counter.  Perhaps the metal plate is
neutralizing all the positive or negative charged particles on that metal foil.
Kind of like the "Zero Stat" guns sold by "Discwasher" for neutralizing the
static on your vinyl audio disks?

Does that sound plausible ? ...Anybody ?