I have an HT-502 connecting my fax machine through Asterisk to Gafachi. T.38 with that setup, using Asterisk’s passthrough feature, works like a charm.
Today, I upgraded to Asterisk 18.104.22.168 in order to do T.38 termination locally as well, but my luck there hasn’t been so great. G.711 from the ATA to * works, but I can’t even get the fax machine to connect with T.38, much less send pages. I get the following messages when I try:
[Jan 5 21:47:41] WARNING: app_fax.c:173 phase_e_handler: Error transmitting fax. result=49: The call dropped prematurely.
[Jan 5 21:47:41] WARNING: app_fax.c:618 transmit: Transmission error
I’m doing the recommended Answer then Wait for 3 seconds in order for the fax tone to signal * to use T.38, and I’ve put temporary debug messages in app_fax.c long enough to determine that T.38 negotiation is working. What I can’t figure out is why fax termination isn’t working.
I’ve tried editing sip.conf according to the troubleshooting section of voip-info.org’s Asterisk T.38 page, but that didn’t work. I would try tweaking things in udptl.conf, but I’m not sure which direction to go there that would make the ATA work with Asterisk’s fax termination without breaking passthrough to Gafachi.