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Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!ihnp4!zehntel!hplabs!hao!seismo!brl-tgr!jcp
From: jcp@brl-tgr.ARPA (Joe Pistritto )
Newsgroups: net.dcom
Subject: Re: Noisy {{~r lines affecting 212A { modems
Message-ID: <7438@brl-tgr.ARPA>
Date: Wed, 16-Jan-85 19:37:23 EST
Article-I.D.: brl-tgr.7438
Posted: Wed Jan 16 19:37:23 1985
Date-Received: Mon, 21-Jan-85 03:47:48 EST
References: <145@pttesac.UUCP>
Reply-To: jcp@brl-tgr.ARPA (Joe Pistritto )
Organization: Ballistic Research Lab
Lines: 15


	The errors you get with the 212A modem are almost all burst
errors, caused by the scrambler/descrambler circuit in the modem.
When any bit is damaged, because of the scrambled nature of the
signal, (which is scrambled in 'groups' of bits (I think 4)), all
of the bits in the group are damaged, typically turning into ones,
hence the high probability of characters with lots of ones in them
(RUBOUT 0177, Tilde 0176, } 0175.  This is one of the worst features
of the 212 design, and renders it practically useless for interactive
lines except where line quality is better than average.  Try VADIC
3400 protocol modems if you can, they don't have this problem (or
many others for that matter...)

						-JCP-
PS: I don't work for VADIC, I just like their stuff.