Yes, tweaking the gain is a wonderful method when curing echo issues. Lee Brent Paddon wrote:
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).
Typically we use cheap little linksys PAP-2T ATA's and have found these to work perfectly.
1/ ensure there is as low a latency as possible and zero jitter. We run QoS on private tails so this isnt too hard. 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) 3/ Ensure there is NO transcoding going on anywhere - even between 711u and 711a - this will break faxing if there is 4/ In the linksys PAP-2T the FXS port gain settings need changing from defaults - we've found -1.5db to work well
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.
Brent
On Sat, Aug 29, 2009 at 3:03 AM, Scott Berkman <scott at sberkman.net <mailto:scott at sberkman.net>> wrote:
Agreed.
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.
-Scott
*From:* voiceops-bounces at voiceops.org <mailto:voiceops-bounces at voiceops.org> [mailto:voiceops-bounces at voiceops.org <mailto:voiceops-bounces at voiceops.org>] *On Behalf Of *Kenny Sallee *Sent:* Friday, August 28, 2009 12:06 PM *To:* voiceops at voiceops.org <mailto:voiceops at voiceops.org> *Subject:* [VoiceOps] FAX over VOIP networks
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.
From our experience, to be most successful w/ FAX over IP of any sort we've found that if you:
1.) Set baud to lowest setting fax can handle
2.) Lower print quality settings if possible
3.) Make sure to force G711
4.) Disable ECM and VAD on fax/modem tone detection
And then cross your fingers fax's are successful and consistent. Anyone else have other experiences or suggestions?
Kenny
_______________________________________________ VoiceOps mailing list VoiceOps at voiceops.org <mailto:VoiceOps at voiceops.org> https://puck.nether.net/mailman/listinfo/voiceops
-- -- Brent Paddon
Director | Over the Wire Pty Ltd brent.paddon at overthewire.com.au <mailto:brent.paddon at overthewire.com.au> | www.overthewire.com.au <http://www.overthewire.com.au> Phone: 07 3847 9292 | Fax: 07 3847 9696 | Mobile: 0400 2400 54 | Direct: 07 3503 4807 ------------------------------------------------------------------------
_______________________________________________ VoiceOps mailing list VoiceOps at voiceops.org https://puck.nether.net/mailman/listinfo/voiceops