T.38 faxing

**eaf** · 12-10-2009 09:49 AM

Does VOIPo support T.38?

I mean, if I have a device that sends/accepts faxes in T.38, VOIPo will correctly get that T.38 stream and will forward it along, right? And this should be pretty much error free, contrary to faxing over G.711?

**chpalmer** · 12-10-2009 09:58 AM

They dont support it. And the PAP2/RT31P2 does not have that available in them either...

I still have my Grandstream 286 that does have that codec and it works every time for me while the neither Linksys will finish the transmission without error...

Otherwise, The guys have some great faxing options....

**eaf** · 12-10-2009 10:07 AM

I wouldn't use just PAP2 for this of course.

But I thought I saw t38 being offered in SDP stream on several occasions...

**chpalmer** · 12-10-2009 10:09 AM

So far what Im using kicks over our Vonage fax line at the offfice sold to us as a fax line...

**VOIPoTim** · 12-10-2009 10:10 AM

Originally Posted by eaf

I wouldn't use just PAP2 for this of course.

But I thought I saw t38 being offered in SDP stream on several occasions...

We don't officially support it.

We use over a dozen upstream carriers and it's only supported by a few, so it would all depend on where the call happens to be routed.

We do offer a completely TDM-based fax solution for both incoming and outgoing faxes that doesn't use our VoIP network.

http://www.voipo.com/fax-to-email.shtml

**chpalmer** · 12-10-2009 10:15 AM

Thanks Tim... I was looking for a specific forum post from earlier this year but that link works...

**chpalmer** · 12-10-2009 10:18 AM

{hijack}

http://dilbert.com/

{/hijack}

**eaf** · 12-10-2009 10:24 AM

Yeah, I know about that solution. Comes with a monthly fee, right?

So when RTP is set to bypass your servers I'm at the mercy of the upstream providers... Same thing when you proxy the audio too?

How do end-user providers that officially support T.38 implement this then? Are they sticking only to those carriers that accept T.38 or are they transcoding and then using internal low-latency paths?

**VOIPoTim** · 12-10-2009 10:50 AM

Originally Posted by eaf

Are they sticking only to those carriers that accept T.38 or are they transcoding and then using internal low-latency paths?

Either of these would work. Transcoding is an option we looked at in the beginning, but it's very resource-intensive.

**fisamo** · 12-10-2009 11:09 AM

IIRC, a Residential user can send a few outgoing FAXes a month with no fee and without raising any 'red flags'. I can't speak for certain right now, because I'm currently subscribed to a FAX line.