12 thoughts on - IAXModem Or T38Modem?

• Personally I use spandsp + res_fax (res_fax.so, res_fax_spandsp.so) and SendFAX/ReceiveFAX applications.

  2014-03-24 8:41 GMT+03:00 Mike Diehl :

• I have to use both. IAXModem is fine for sending but receives garbage, and T38Modem is fine for receiving but treats all outgoing calls as busy.

• Hi Mike,

  Am Montag, den 24.03.2014, 01:41 -0400 schrieb Mike Diehl:

  It depends on Your environment and Your asterisk version. If Your connection to the PSTN is via ISDN (eg. channel via DAHDI or CAPI), You should use IAXmodem. The fax is transferred on the audio layer and there is no need to translate it into T.38. If Your connection is via some VoIP Provider using T.38 or via a Mediagateway like BeroFix, You should use T38Modem.

  Newer versions of asterisk have additional features regarding T.38
  (AFAIK). In this case there may be no need for any of the modems.

  HTH,

  Karsten

• We use IAXModem-1.2.0 built from source and packaged as an rpm using mock/rpmbuild together with Hylafax+-5.5.3 from epel. Since April 2013 this combination has been running two dedicated POTS lines through a TDM800-p8 on our Atom CentOS-6.3 based Asterisk-11.7.0 (current version) box without any reported difficulties (once I sorted out the upstart stanzas).

  As this is the only combination I have experience with it is the only one I
  can recommend. But it has proven very reliable so far as I am aware and I
  would be made aware pretty quickly if it was not.

• Hi,

  we are using T38modem, it was a long way to get it stable, but finally it works quite good with 10 parallel running T38modems.

  But your carrier has to support T38, when we began to evaluate this some years ago, this was not true for all.

• Would you share the provider you are using? I have had almost zero luck so far.

  Thanks,

  j

• What country are you in? Every carrier we

• Sorry – should have mentioned USA. I say “almost” zero luck, because I
  have managed to get a few faxes out with a handful of providers tested, but none consistently. If anyone is very happy with their T.38 provider, please email me off list.

  I got the spam message. At least she is cute.

  Cheers,

  j

• I would not say “happy”, since there is no happiness in a world with T.38, but Level 3 supports T.38. Level 3 is wholesale only as far as I know.

  Vitelity has some fax service stuff too.

  —–Original Message—

• In my experience iaxmodem + Hylafax is very stable and work in my setups fine.

  But in these setups I either use ISDN uplinks or SIP trunks with low RTT
  and jitter (highspeed links to the service provider, no WAN links). Thus, T38 is in my setups not necessary.

  regards Klaus

• I wouldn’t mind if someone posted on the list a known working provider with the proper configuration to use T.38. In my case I don’t consider it an issue with the provider because they sent the proper T.38 Invite, but Asterisk IMO does not know how to handle it.

• j> I wouldn’t mind if someone posted on the list a known working provider j> with the proper configuration to use T.38. In my case I don’t consider j> it an issue with the provider because they sent the proper T.38
  j> Invite, but Asterisk IMO does not know how to handle it.

  Are you using a single credential-tuple with the provider?

  If the provider supports T.38 and if you can separate out fax lines, there is no need to stick asterisk between them and t38modem. Just have t38modem access the provider directly. Hylafax will handle the rest.

  (Look for things like sub-account, peer and/or trunk configs.)

  -JimC