Faxes

WARNING: this is an automatic post retrieved from the Asterisk-Users Mailing List, not an authored post Mailing-list Collector September 03, 2010 Asterisk-Users 9 Comments

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We have asterisk connected to the PSTN VIA TE410P (ANSI SS7 to T1 PRI)
cards.

I am having trouble completing faxes. Carrier send calls to me using SIP.
Any recommendation to have some success with Fax.

We trying using T.38 pass through and using G711U codec.

Asterisk Version 1.6.1.1

Thanks,

Dave

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9 Responses to “Faxes”

  1. Steve Totaro said:

    Sep 03, 10 at 11:08 am

    Dave,

    T.38 in some fashion.

    But you don’t really explain your call flow or what you are trying to
    do. You say you have PSTN and then talk about SIP. Are you just
    trying to pass the calls to physical FAX machines, or a server to
    handle faxing?

    Elaborate a bit and I am sure someone can offer some advice.

    Thanks,
    Steve Totaro

  2. "dave george" said:

    Sep 03, 10 at 11:50 am

    The asterisk box is connected to the PSTN using TE410 cards. Asterisk talk
    SS7 to the PSTN. On the IP side I use SIP. I terminate calls onto the
    PSTN.

    The carrier sending the calls wants me to be able to pass faxes to physical
    fax machines on the PSTN. So far they are failing.

    We just want ot be able to pass faxes using g711u or t.38 pass through.

    Thanks,
    Dave

  3. David Backeberg said:

    Sep 03, 10 at 1:39 pm

    You don’t say the percentage that are failing. However, people who
    have worked with SIP on asterisk have been known to do:

    exten => s,1,Playback(silence/1)
    exten => s,n,Whatever(is_next)

    And I don’t know why, but this seems to make things better.

    If you’re doing an Answer and then a receive_Fax, try putting a
    playback silence in between and see if that helps anything.

  4. "dave george" said:

    Sep 03, 10 at 1:58 pm

    All my attempts are failing.

    Thanks
    Dave

  5. "Danny Nicholas" said:

    Sep 03, 10 at 2:09 pm

    Can you post the dialplan snippet you are using?

  6. "Kevin P. Fleming" said:

    Sep 03, 10 at 2:17 pm

    As I told you on the asterisk-ss7 list, you can’t ‘pass through’ T.38,
    because the PSTN does not speak T.38. If one side of the call is SIP,
    and the other side is TDM, then you have only two choices: pass the call
    through in audio mode (FAX over VoIP), or act as a T.38 gateway (FAX
    over T.38).

    At this time, the only option without patching Asterisk is to pass the
    call through in audio mode, but there are many, many problems with doing
    FAX over VoIP (Steve Underwood’s page on the soft-switch.org site
    explains them very well).

    There are patches in the issue tracker at issues.asterisk.org to add
    T.38 gateway functionality to various releases of Asterisk, and they
    work well for quite a few people. If you added that, you’d be able to
    act as a T.38 gateway, which would dramatically increase your chances of
    success.

  7. "dave george" said:

    Sep 03, 10 at 2:32 pm

    Thanks Kevin,

    I tried passing it over VOIP using g711U codecs with no success. I will try
    using the patches that you mentioned and post the results.

    Thanks,
    Dave

  8. Joel Maslak said:

    Sep 03, 10 at 6:03 pm

    g711 across a network without perfect jitter/delay characteristics will not
    work.

    You cannot do g711 faxing across the internet – at all.

    It’s not a perfect solution even in an office on a dedicated LAN environment
    (you’ll still get failed faxes).

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  9. Nasir Iqbal said:

    Sep 03, 10 at 10:44 pm

    Try open souce solution “ICTFAX” for T.38 faxing developed by us available
    at http://www.sourceforge.net/projects/ictfax

    Nasir Iqbal

    ICT Innovations
    http://www.ictinnovations.com/

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