Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!hplabs!pyramid!lstowell
From: lstowell@pyrnova.pyramid.com (Lon Stowell)
Newsgroups: comp.dcom.modems
Subject: Re: New Modems
Message-ID: <136549@pyramid.pyramid.com>
Date: 4 Dec 90 21:42:32 GMT
Sender: daemon@pyramid.pyramid.com
Reply-To: lstowell@pyrnova.pyramid.com (Lon Stowell)
Organization: Pyramid Technology Corp., Mountain View, CA
Lines: 28

In article <2038@mountn.dec.com> hall@state.enet.dec.com writes:
>EIA/TIA standard 496-A.  The baseline tests used by PC Magazine simulated
>a typical U.S. long-distance circuit, with the following impairment levels:
>
>Input level:	-10 dBm
>Output level:	-23 dBm
>IMD, 2nd-level:	 52 dB
>IMD, 3rd-level:  50 dB
>Frequency shift: 1.25 Hz
>Phase jitter:	 8 degrees
>
>No level for white noise was given (should have been about 32 dBrn), nor

Those are pretty benign impairment levels for a V.32 modem.
Most I have tested (With the TAS 1010) tolerate CONSIDERABLY
more noise than that...including single tone interference only a
few dB below xmitter level at 1004, 2600, 1800 Hz...

What DOES separate the world-class V.32's from the commodity
products is their ability to tolerate amplitude jitter and phase
roll (loosely described as an echo that is constantly being
shifted in phase...) typical on satellite or transoceanic
connections...although BOTH of these impairments are pretty rare
in North America..and quite common on international circuits.

Have yet to find a V.32 that can tolerate Gain Hits of more than
a dB or so..even if the change results in staying totally within
the dynamic range of the partner's receivers....