Path: utzoo!mnetor!uunet!husc6!mailrus!nrl-cmf!ames!pacbell!att-ih!ihnp4!ihuxv!tedk
From: tedk@ihuxv.ATT.COM (Kekatos)
Newsgroups: sci.electronics
Subject: Re: Library book detectors.
Message-ID: <2536@ihuxv.ATT.COM>
Date: 23 Mar 88 16:25:28 GMT
References: <5398@swan.ulowell.edu| <1261@uop.edu| <2521@ihuxv.ATT.COM| <1674@uhccux.UUCP> <20719@bu-cs.BU.EDU> <2530@ihuxv.ATT.COM> <1574@sigma.UUCP>
Reply-To: tedk@ihuxv.UUCP (55624-Kekatos,T.G.)
Distribution: na
Organization: AT&T Bell Laboratories - Naperville, Illinois
Lines: 37

In article <1574@sigma.UUCP> bill@sigma.UUCP (William Swan) writes:
>In article <2530@ihuxv.ATT.COM> tedk@ihuxv.UUCP (Kekatos,T.G.) writes:
>>Does anyone know of the history of using L-C circuits. I heard
>>that they were used in WWII. The term "Friend or Foe" circuit
>>comes to mind. 
>
>The use of "L-C" circuits goes a ways back.. but not as IFF (Identification
>Friend or Foe) gear. 
>
>IFF equipment was essentially a transponder device, designed to reply with
>a coded radio sequence upon (as I recall) radio interrogation. 

Something like modern radio-transponder equipment in most airplanes.


>My father worked on this stuff for a while during WWII, and said it was a
>bear to service, it was all wired with white wires with thermite charges
>distributed throughout, and a .38? shell set up at one end of the chassis
>to fire through all the vacuum tubes should self-destruct be required. Once
>in a while, of course, a particularly difficult module would accidentally
>misfire, making servicing it a moot point... :-)
>

I wonder if this kind of explosive "copy-protection" is still
being used in today's miltary and defense electronics. 

>
>William Swan  {ihnp4,decvax,allegra,...}!uw-beaver!tikal!sigma!bill





Ted G. Kekatos
backbone!ihnp4!ihuxv!tedk                     (312) 979-0804
AT&T Bell Laboratories, Indian Hill South, IX-1F-460
Naperville & Wheaton Roads - Naperville, Illinois. 60566 USA