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From: randolph@cognito.UUCP
Newsgroups: comp.dcom.telecom
Subject: Re: Submission for mod.telecom (Modems and data jacks)
Message-ID: <8704162250.AA22899@cognito.sun.com>
Date: Thu, 16-Apr-87 17:50:14 EST
Article-I.D.: cognito.8704162250.AA22899
Posted: Thu Apr 16 17:50:14 1987
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Reply-To: randolph@sun.UUCP (Randolph Fritz <sun!randolph>)
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At the end of a very good informative article on RJ-41 & RJ-45, Larry Lippman 
(larry@kitty.UUCP) writes:

>	While I don't want to get off on a tangent here, the fact is that
>transmitting at a higher level is NOT necessarily going to result in a lower
>error rate.  I can vouch for this from extensive personal experience.
>Most of the newer modems have receive threshholds of < -40 dBm; this is
>really quite a bit of sensitivity.  Transmitting at a higher-than-necessary
>level can "strain" the ability of the band-pass filters in the modem to
>reject the locally-generated transmit signal, and leakage of the transmit
>signal into the modem receiver can often exacerbate a data line error
>situation.
>	So the moral is: LOUDER is not always BETTER. :-)

Moreover, some telco equipment does *not* have automatic gain control
and cannot handle "hot" levels.  This is especially a problem with
older frequency-muliplexors -- the high levels cause overmodulation
and the hot signal inteferes with adjacent signals on the same
carrier.  (I wonder: was this why telcos used to insist on Data Access 
Arrangements?)
--
Randolph Fritz
sun!randolph
randolph@sun.com