[Asterisk-Dev] T.38 pass-through / T.38 support

Matthew Boehm mboehm at cytelcom.com
Fri Jun 3 12:39:36 MST 2005

Steve Underwood wrote:
> They must be bypassing * then. * has no way to pass-through a UDPTL
> stream right now. I don't see how it would even bypass a T.38 stream,
> though. It lacks the ability to negotiate one.

I know you find it hard to believe Steve, but I guarantee you this is what

Caller on PSTN dials ATA fax. Call is routed to AS5300 over PRI. Call
becomes T38. 5300 sends call to Asterisk and on to ATA via SIP. The warning
messages about UDPTL t38 that I said previously display during the transfer
of the fax. Call completes and fax looks great.


Call originates from ATA. Asterisk sends call to 5300. 5300 says its T38.
The 5300 will, depending on if local or LD call, terminate either PRI to
PSTN or to carrier via H323. Call completes and fax looks great.

All of it goes thru asterisk at some point.


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