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  • Aykut, Wed 01 of Aug, 2007 [07:53 UTC]: Hi all, does anybody know about Thomson ST2030 SIP phone. I have upgraded it to latest version (1.56) but "Hold" and "Conf" features are not working after the upgrade ?? Do you know any solution or do you have Ver. 1.52 ?? Where can I find it?
  • Edward J Brown, Tue 31 of Jul, 2007 [23:33 UTC]: Has anybody experienced Choppy voice quality when using a Linksys SPA942 in an Asterisk Conference bridge? It works fine with my polycom and Cisco, but sucks with my Linksys.
  • www.astawerks.com, Fri 27 of Jul, 2007 [18:00 UTC]: does anyone use asterisk on top of clark connect? does it work good?
  • simon, Fri 27 of Jul, 2007 [14:16 UTC]: Hi All, Has anyone here managed to get the Cisco79x1 to successfully fail over to the backup proxy. I have 2 asterisk servers , handsets all register and function, except that backup proxy function doesn't work. Any working example would be very apprecia
  • Matthew Richmond, Thu 26 of Jul, 2007 [03:40 UTC]: using the page() application to page across our building...often the meetme conferences don't disconnect after the caller hangs up. Anyone else having this problem. (using Polycom phones)
  • Matthew Richmond, Wed 25 of Jul, 2007 [02:58 UTC]: thanks Nicholas Blasgen! I haven't worked with AGI before, but there's always a first! Thanks again!
  • Nicholas Blasgen, Tue 24 of Jul, 2007 [19:18 UTC]: Matthew Richmond, AGI will handle all that for you.
  • sam, Mon 23 of Jul, 2007 [16:39 UTC]: need help - certain voicemail extension will stop working and recording voicemail on asterisk - anyone know why and how to fix it? Thanks
  • john haji, Mon 23 of Jul, 2007 [14:55 UTC]: free calls to pakistan
  • bong, Sat 21 of Jul, 2007 [19:09 UTC]: hi good day to all can anyone help me how to configured the nortel sip to the signaling server and how to activate in mobile w/ sip compatible without mcs
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T.38

T.38 is an ITU standard for sending FAX accross IP networks in a real-time mode.
FAX messages are sent as UDP or TCP/IP packets.

  • The IETF RFC RFC 3362 implements a media type called image/t38 for T.38 faxes.

From RFC 3362:

ITU-T Recommendation T.38 T.38 describes the technical features necessary to transfer facsimile documents in real-time between two standard Group 3 facsimile terminals over the Internet or other networks using IP protocols. The Recommendation allows the use of either TCP or UDP depending on the service environment.

ITU-T Recommendation T.38 T.38 Annex D describes system level requirements and procedures for internet aware facsimile implementations and internet aware facsimile gateways conforming to ITU-T T.38 to establish calls with other ITU-T T.38 implementations using the procedures defined in IETF RFC 2543 SIP-99 and IETF RFC 2327 SDP.

Note that ITU-T T.38 Recommendation T.38 (04/02) T.38 is an aggregation of the original ITU-T Recommendation T.38 (06/98) T.38-98 and all of the subsequent Amendments and Corrigendum including T.38D-00. While T.38 and T.38D-00 describe SIP procedures per SIP-99, the procedures can also be applied to the revised Session Initiation Protocol specification SIP.



T.38 - protocol or Codec?

Seems like T.38 can be used as a FoIP protocol by itself, running over UDP. It is also adapted to be included as image/t38 in a SDP attached to a SIP Invite - this way running as a "codec".

T.38 with Asterisk (initial work)

I am not sure how long it may take, but we made a little progress on this protocol. Feel free to check http://www.ionidea.ua/oss/asterisk/
Looking for some input, so we can proceed with it, as well as extra help.

<Aug 26 2005> We have little progress on the stack implementation. You can find latest (but still unstable) code at http://www.ionidea.ua/oss/asterisk/

T.38 with Asterisk (Attractel commercial solution)

A full fledged t.30 and t.38 stack for asterisk (both passthrough, termination and gateway) is available from Attractel
As the software is not under GPL, this can be used together with other non GPL parts of asterisk, such as g729 or iLBC.
The software comes with ITU t.30 modems : v.21, v27ter, v29, v17 and includes standalone FAX transmit and receive programs for use in fax2email and email2fax gateways.

T38 with CallWeaver (supported)

The initial efforts to support T38 in Asterisk via the SpanDSP library have beed frustrated by license issues as SpanDSP is GPL licensed and thus incompatible with Digium's dual licensing regime. This has led to the developers using CallWeaver for their integration and development work, in effect abandoning any further work on Asterisk-SpanDSP integration.

As a result, CallWeaver has emerged a the undisputed leader in T38 support. CallWeaver has mature support for both T38 passthrough and T38 termination. A developer branch has T38 gateway functionality working as well but this has not yet been released. A new module, app_faxdetect has beed added to support fax detection over SIP channels and many T38 supporting SIP devices have been extensively tested for compatibility, amongst them Cisco, Patton, Quintum and many others.

CallWeaver was forked from the Asterisk 1.2 code base and therefore Asterisk users who need reliable T38 support will find it easy to migrate to CallWeaver. More information about CallWeaver can be found on the OpenPBX.org page or at wiki.openpbx.org

OpenPBX 1.2rc3 currently supports T.38 in passthrough and endpoint modes. In addition, OpenPBX Trunk supports gateway mode as of revision 2568 with spandsp snapshot 20070329

T38 with T38modem

What is t38modem from www.openh323.org?
  • From your fax application view point it's a fax modem pool.
  • From IP network view point it's a H.323 endpoint with T.38 fax support.
  • From your view point it's a gateway between a fax application and IP network.

See also


Created by jht2, Last modification by spamblock on Sat 05 of May, 2007 [08:28 UTC]

Comments

Comments Filter

Looking for

by Jeff Dubin on Tuesday 12 of June, 2007 [14:27:27 UTC]
I'm looking for a virtual t.38 fax modem for windows which would talk, via SIP, directly to a t.38-enabled VoIP provider. It shouldn't require an enterprise-scale purchase — my goal is for individual use only, something which wouldn't require local dedicated hardware (i.e. *, cisco, etc., not necessary on my end). Any ideas? Thanks!

PS — The closest I've come is t38modem, related to the openh323 project, and they don't (yet) provide compiled windows binaries.

Can T.38 talk to a "regular" fax?

by Amos Shapira on Thursday 21 of September, 2006 [05:53:42 UTC]
If I bother to get myself something that can convert my fax (an HP PSC 2410 all-in-one thingy) to T.38 - would it be able to talk to "regular" PSTN faxes on the other side of the call or will I need to find some T.38-enabled "end point" to convert things back to PSTN faxes?

Multipages fax

by czuker on Tuesday 28 of March, 2006 [17:25:40 UTC]
Are you able to send multipages fax with latest version of span dsp? Which hardware are you using? Which version of asterisk are you using?

It is working.... almost

by rublev on Friday 22 of July, 2005 [19:08:54 UTC]
I can say the solution is in 50% of completion... so would like to see if it is really needs for the people (in $$$).

vasyl dot rublyov at ionidea dot com

Edit

When it works

by Anonymous on Tuesday 05 of October, 2004 [22:45:58 UTC]
When they get it working it will be a great solution(:frown:)

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