Incoming Fax over SIP Trunk

I’m running A@H 2.8 with freePBX 2.1.0.

If I connect a regular fax machine to a phone adapter that is configured to work with my Asterisk as an extension, then dial 7777 to simulate an incoming call, the fax tones are detected and the fax is sent without a problem.

When faxing from “the outside” coming across a SIP trunk (no PSTN lines or cards), the fax tones are not detected and the hello recording is played as if it is a regular voice call - the fax fails.

Any ideas?

Fax is un-reliable on VoIP, and won’t work at all if using a lossy codec. It could also be inadequate time to detect the fax, etc. Routing the line directly to the fax context so it doesn’t have to go through the detection process, and make sure you are running g.711u for your codec. That’s a start.


As a newbie with the exact same problem…did you fix this yet? If so, can you tell me how please?