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Yes, tweaking the gain is a wonderful method when curing echo issues.<br>
<br>
Lee<br>
<br>
Brent Paddon wrote:
<blockquote
cite="mid:ad139bd20908281153o457f9437p788f860ce3f4de3a@mail.gmail.com"
type="cite"><br>
I've spent more time playing with fax over IP networks than I would
care to remember. Here's what we ended up doing (in Australia anyway).<br>
<br>
Typically we use cheap little linksys PAP-2T ATA's and have found these
to work perfectly.<br>
<br>
1/ ensure there is as low a latency as possible and zero jitter. We
run QoS on private tails so this isnt too hard.<br>
2/ we dont run T38 but instead ensure that all codecs in use along the
entire path are g711A (711A is the PSTN standard here)<br>
3/ Ensure there is NO transcoding going on anywhere - even between 711u
and 711a - this will break faxing if there is<br>
4/ In the linksys PAP-2T the FXS port gain settings need changing from
defaults - we've found -1.5db to work well<br>
<br>
This last bit has been very important, otherwise for us the Linksys was
providing too 'loud' a signal to the fax machine and would break faxing
after say a page or two max. Using these settings, we have customers
who send long (15-20) page faxes regularly with no problems.
Additionally so far we havent had to change any fax machine settings,
presumably the fax machines are simply training down to a speed they
are happy with but we haven't spent much time looking at what they do
in this regard - faxing works and thats all we cared about.<br>
<br>
Brent<br>
<br>
<div class="gmail_quote">On Sat, Aug 29, 2009 at 3:03 AM, Scott
Berkman <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:scott@sberkman.net">scott@sberkman.net</a>></span>
wrote:<br>
<blockquote class="gmail_quote"
style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div link="blue" vlink="purple" lang="EN-US">
<div>
<p><span style="font-size: 11pt; color: rgb(31, 73, 125);">Agreed.</span></p>
<p><span style="font-size: 11pt; color: rgb(31, 73, 125);"> </span></p>
<p><span style="font-size: 11pt; color: rgb(31, 73, 125);">The key
really is g.711 (usually u-law) and low (read no)
latency/jitter unless you can fully interop T.38 across the network.
Most
fax machines will auto-negotiate to the lower speeds when needed, but
low to
middle end Brother machines may be a major exception as they often have
a poor
T.30 implementation.</span></p>
<p><span style="font-size: 11pt; color: rgb(31, 73, 125);"> </span></p>
<p><span style="font-size: 11pt; color: rgb(31, 73, 125);">
-Scott</span></p>
<p><span style="font-size: 11pt; color: rgb(31, 73, 125);"> </span></p>
<div
style="border-style: solid none none; border-color: rgb(181, 196, 223) -moz-use-text-color -moz-use-text-color; border-width: 1pt medium medium; padding: 3pt 0in 0in;">
<p><b><span style="font-size: 10pt;">From:</span></b><span
style="font-size: 10pt;">
<a moz-do-not-send="true"
href="mailto:voiceops-bounces@voiceops.org" target="_blank">voiceops-bounces@voiceops.org</a>
[mailto:<a moz-do-not-send="true"
href="mailto:voiceops-bounces@voiceops.org" target="_blank">voiceops-bounces@voiceops.org</a>]
<b>On
Behalf Of </b>Kenny Sallee<br>
<b>Sent:</b> Friday, August 28, 2009 12:06 PM<br>
<b>To:</b> <a moz-do-not-send="true"
href="mailto:voiceops@voiceops.org" target="_blank">voiceops@voiceops.org</a><br>
<b>Subject:</b> [VoiceOps] FAX over VOIP networks</span></p>
</div>
<div>
<div class="h5">
<p> </p>
<p>So the last thread on T38 made me want to start a thread on
FAX over IP via an ATA or something like the Adtran TA900 series.</p>
<div>
<p> </p>
</div>
<div>
<p>From our experience, to be most successful w/ FAX over IP of
any sort we've found that if you:</p>
<div>
<p> </p>
</div>
<div>
<p>1.) Set baud to lowest setting fax can handle</p>
</div>
<div>
<p>2.) Lower print quality settings if possible</p>
</div>
<div>
<p>3.) Make sure to force G711</p>
</div>
<div>
<p>4.) Disable ECM and VAD on fax/modem tone detection</p>
</div>
<div>
<p> </p>
</div>
<div>
<p>And then cross your fingers fax's are successful and
consistent. Anyone else have other experiences or suggestions?</p>
</div>
<div>
<p>Kenny</p>
</div>
</div>
</div>
</div>
</div>
</div>
<br>
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<br>
</blockquote>
</div>
<br>
<br clear="all">
<br>
-- <br>
--<br>
Brent Paddon<br>
<br>
Director | Over the Wire Pty Ltd <a moz-do-not-send="true"
href="mailto:brent.paddon@overthewire.com.au">brent.paddon@overthewire.com.au</a>
| <a moz-do-not-send="true" href="http://www.overthewire.com.au">www.overthewire.com.au</a><br>
Phone: 07 3847 9292 | Fax: 07 3847 9696 | Mobile: 0400 2400 54 |
Direct: 07 3503 4807<br>
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</blockquote>
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