[asterisk-users] fxotune vs rxgain/txgain

[Matt Watson]

In short, fxotune adjusts line impedance, where as adjusting gains I believe 
is essentially adjusting the amplification / deamplification of the signal.

http://www.voip-info.org/wiki/view/Asterisk+fxotune

-- 
Matt Watson
http://www.mattgwatson.ca

On June 6, 2008 12:43:51 am Noah Miller wrote:
> Hi All -
>
> I hope somebody can clarify for me what exactly fxotune does, and how
> it is related to gain settings.  I've been reading what appears to be
> conflicting information from various sources.
>
> I've got a box with an AEX800 with 6 lines (from Qwest) running
> asterisk and zaptel versions 1.4.20.1 and 1.4.11 respectively.  We've
> been experiencing some echo/quality issues on certain calls which seem
> to happen on all 6 of the lines.  I manually calibrated the
> rxgain/txgain using ztmonitor and a milliwatt test line to the
> somewhat improbable levels of +10.0/-2.0 (about the same for all 6
> lines).  These settings yield acceptable call volumes, but echo and
> noise are problems.
>
> If I run fxotune, it gives me the following numbers:
>
> 1=10,0,0,0,0,0,0,0,0
> 2=12,0,0,0,0,0,0,0,0
> 3=12,0,0,0,0,0,0,0,0
> 4=10,0,0,0,0,0,0,0,0
> 5=10,0,0,0,0,0,0,0,0
> 6=10,0,0,0,0,0,0,0,0
>
> Two questions here:
>
> 1) What do these numbers mean?  Are they in any way related to either
> rxgain or txgain?
> 2) Am I supposed to set rxgain and txgain back to 0 if I use fxotune -s?
>
> If I do use these fxotune settings and set rxgain and txgain to zero,
> the volume on incoming zap calls is almost too low to be heard, but
> echo issues seem to be solved.
>
> Do I have to choose between 1) acceptable call volume with echo or 2)
> super-quiet call volume without echo?  Should I petition Qwest to
> install a repeater?
>
>
> Thanks,
> Noah
>
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