<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 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>
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<p><b><span style="font-size: 10pt;">From:</span></b><span style="font-size: 10pt;">
<a href="mailto:voiceops-bounces@voiceops.org" target="_blank">voiceops-bounces@voiceops.org</a> [mailto:<a 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 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></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>
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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 href="mailto:brent.paddon@overthewire.com.au">brent.paddon@overthewire.com.au</a> | <a href="http://www.overthewire.com.au">www.overthewire.com.au</a><br>
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