[Asterisk-Users] Fax and PRI

[Keith Burns]

In a previous company, we had issues with selling "Fax-o-IP" services
varying from the ability of CPE to support the correct NSE values and
recognize the difference between G3 ("standard" fax) and Super G3 ("more
like a modem" fax) through to the gateway's ability to turn echo-can's
on and off based on the fax type.

Fax is SOOOOO sensitive to packet-loss, NSE response, the
disabling/enabling of echo-can's based on G3/Super-G3... 

I have a pretty decent white paper I found on this subject I can forward
to those that are interested offline (kburns at cartwheelglxy.com)



> -----Original Message-----
> From: asterisk-users-bounces at lists.digium.com [mailto:asterisk-users-
> bounces at lists.digium.com] On Behalf Of Lee Howard
> Sent: Wednesday, January 19, 2005 6:46 PM
> To: Jon Radon
> Cc: Asterisk Users Mailing List - Non-Commercial Discussion
> Subject: Re: [Asterisk-Users] Fax and PRI
> 
> On 2005.01.19 17:06 Jon Radon wrote:
> > I use a Multi-Tech Multimodem ZPX and a Sipura SPA-2000 along with
> > Hylafax.  On the Asterisk end I'm using X100P's.  This has worked
> > flawlessly for me thus far.  Some tips of my success.
> >
> > 1.)  Fax detect on the Sipura breaks faxing.  Strange, I know.
> > 2.)  Tuning your txgain and rxgain both on the Sipura and on the
> > Zaptel line is imperative.
> >
> > Originally with this setup I was getting all kinds of bad frames.
> > After tweaking my faxes are squeaky clean.
> 
> Thanks for these tips it reminded me that I still hadn't looked in on
> the FXS port ("line") settings on the SPA.  (I don't receive many
faxes
> on this setup, so it hasn't been a priority.)
> 
> As it turns out, disabling silence suppression, echo cancellation,
echo
> suppression, and all of the "fax" features did the trick.  Now I'm
> receiving faxes fine.
> 
> I did also have to disable V.34-Fax on the HylaFAX-controlled modem.
> 
> I didn't have to adjust any of the gain controls, although I already
> had adjusted the FXS port impedence a long time ago.
> 
> Lee.
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