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From: jabusch@osiris.cso.uiuc.edu (John Jabusch)
Newsgroups: sci.military
Subject: Re: IFF
Message-ID: <1991Jan24.040748.23014@cbnews.att.com>
Date: 24 Jan 91 04:07:48 GMT
References: <1991Jan19.041005.4675@cbnews.att.com>
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From: jabusch@osiris.cso.uiuc.edu (John Jabusch)
jae@sybil.cs.Buffalo.EDU (Jae Hoon Lee) writes:



>From: jae@sybil.cs.Buffalo.EDU (Jae Hoon Lee)
>How does IFF on the fighters work?  

IFF Transponders automatically sense what mode they're being interrogated
in, using a pulse-train timing pattern.  Mode determination complete, a
reply is formed based on information being fed to the transponder.  In the
case of Modes 1, 2, and 3a, this is key-punched or thubm-wheeled in by
the pilot or ground technician.  Mode C (altitude info) usually comes from
one of the on-board altimeter systems.  Mode 4 (secure mode) is usually
handled by a special box which examines the Mode 4 interrogation, and
then applies a special algorithm to determine a valid reply.

IFF Interrogators will interrogate in any mode selected by the pilot /
navigator / tower operator.  Mode 4 requires a special box, also, which
is used to formulate the interrogation, which only the "crypto" units
know how to handle.

I provided this as very basic information, since your question was fairly
open.

--

John W. Jabusch					US Army Construction
INTERNET: jabusch@cerl.cecer.army.mil    	Engineering Resesarch Lab
MILNET: jabusch@osiris.arpa        		Champaign, IL
"Why waste time learning, when ignorance is instantaneous?" - Hobbes