Path: utzoo!mnetor!uunet!husc6!bbn!mit-eddie!uw-beaver!tikal!sigma!bill
From: bill@sigma.UUCP (William Swan)
Newsgroups: sci.electronics
Subject: Re: Library book detectors.
Message-ID: <1574@sigma.UUCP>
Date: 21 Mar 88 20:38:20 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>
Reply-To: bill@sigma.UUCP (William Swan)
Distribution: na
Organization: Summation Inc, Kirkland WA
Lines: 21

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. 

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... :-)


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