Article View: sci.electronics
Article #17496Re: Library Book detectors
From: ee251aaz
Date: Wed, 22 Apr 1987 05:51
Date: Wed, 22 Apr 1987 05:51
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In article <17024@sun.uucp> cmcmanis@sun.uucp (Chuck McManis) writes: >In article <2835@mit-hermes.AI.MIT.EDU>, jpexg@mit-hermes.AI.MIT.EDU (John Purbrick) writes: >> 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 occured to me reading this that the 'deactivation' may be nothing more >than charging up the capacitor in the LC circuit... > >comments? This is a nice idea, but I could swear that I have repeatedly entered and exited similarly equipped libraries here carrying books I checked out weeks prior. The capacitive circuit would need to possess an incredibly long time constant for this to be possible. It would seem somewhat impractical to design a security system that did not allow you to re-enter (or exit thereafter) the library with a book you checked out some time before. I hope there is someone out there who knows the answer.... Gregory Breit Department of Applied Mechanics and Engineering Science University of California, San Diego
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arc1-ca.pugleaf.net!utzoo!utgpu!water!watmath!clyde!rutgers!ames!ucbcad!ucbvax!sdcsvax!sdcc6!sdcc3!ee251aazReferences:
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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!ames!ucbcad!ucbvax!sdcsvax!sdcc6!sdcc3!ee251aaz From: ee251aaz@sdcc3.UUCP Newsgroups: sci.electronics Subject: Re: Library Book detectors Message-ID: <3875@sdcc3.ucsd.EDU> Date: Wed, 22-Apr-87 00:51:55 EST Article-I.D.: sdcc3.3875 Posted: Wed Apr 22 00:51:55 1987 Date-Received: Fri, 24-Apr-87 00:01:13 EST References: <959@obelix.UUCP> <1104@nonvon.UUCP> <5941@pur-ee.UUCP> <2835@mit-hermes.AI.MIT.EDU> <17024@sun.uucp> Reply-To: ee251aaz@sdcc3.ucsd.edu.UUCP (Gregory Breit) Organization: University of California, San Diego Lines: 23 Summary: Maybe it's not an LC circuit...