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From: jpexg@mit-hermes.UUCP
Newsgroups: sci.electronics
Subject: Re: Stolen item-detectors (Was: Re: Laser eavesdropping)
Message-ID: <2835@mit-hermes.AI.MIT.EDU>
Date: Fri, 17-Apr-87 21:10:39 EST
Article-I.D.: mit-herm.2835
Posted: Fri Apr 17 21:10:39 1987
Date-Received: Sat, 18-Apr-87 19:08:04 EST
References: <959@obelix.UUCP> <1104@nonvon.UUCP> <5941@pur-ee.UUCP>
Organization: MIT AI Lab, Cambridge, MA
Lines: 16
Summary: A different library's books will look stolen!

In article <5941@pur-ee.UUCP>, wn9nbt@pur-ee.UUCP (Dave Chasey) writes:
> 
> I have always wondered about these alarms also.   The ones mentioned
> here seem to involve clips that are removed, or the ones that the
> ones that are destroyed when you pay for the item.  How about the
> ones that are in Library books in some libraries ?  They are
> able to activate the sensor when the book is on the shelf and deactivate
> it when you check the book out. 

My girlfriend visited a library at MIT with me a while ago, and she was
carrying a book (legally obtained) from a different college's library.
As we left through the stolen-book detector, the beeper went off. It 
turned out that the "foreign" book was setting the thing off; the desk
person ran the offending book through the deactivator, and we had no more
trouble. So the deactivation is apparently only for certain frequencies
or codes.