[VoiceOps] FAX over VOIP networks

[Lee Riemer]

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
>
>
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>
>
>
> -- 
> --
> 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
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