Article View: sci.electronics
Article #17522Re: Library Book detectors
From: kunert
Date: Mon, 27 Apr 1987 18:22
Date: Mon, 27 Apr 1987 18:22
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In article <1726@kitty.UUCP>, larry@kitty.UUCP (Larry Lippman) writes:
> Now, THINK, people! How does this system work??? It's really
> rather clever! If no one guesses the correct answer, I'll post it in a
> week.
>
I worked in a library that used a similar system, but there was no way
to deactivate the sensor. The "tag" inserted in the book was just a
printed loop connected to a printed capacitor forming a resonant circuit-
the system was designed so that the library employee would pass the books
around the sensor at the checkout.
Anyway, in the systems that *can* be deactivated, I believe the mechanism
used at the checkout is a simple magnetizer/demagnetizer. My best guess
is that a reed switch is being used to short out the tuned circuit.
--
ihnp4-\ "I'm looking for a lifestyle
Dick Kunert seismo!uwvax!nicmad!kunert that doesn't require my
decvax-/ presence..."
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Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: arc1-ca.pugleaf.net!utzoo!utgpu!water!watmath!clyde!rutgers!husc6!uwvax!astroatc!nicmad!kunert From: kunert@nicmad.UUCP Newsgroups: sci.electronics Subject: Re: Library Book detectors Message-ID: <1640@nicmad.UUCP> Date: Mon, 27-Apr-87 14:22:08 EDT Article-I.D.: nicmad.1640 Posted: Mon Apr 27 14:22:08 1987 Date-Received: Wed, 29-Apr-87 01:21:54 EDT References: <146@illusion.UUCP> <868@oliveb.UUCP> <1726@kitty.UUCP> Organization: Nicolet Instrument Corp., Madison, WI Lines: 20 Summary: my best guess