How can I use the same line for fax and phones with Free Fax for Asterisk?
I want to detect first the fax, and if it isn’t a fax the call must be routed to my SIP extension. Currently I can receive fax only with fax detection turned off and routing the call only to the fax recipient.
No way to answer this question. You didn’t tell us anything about your system.
You posted this in general help so I assume you installed FFA on some type of manually built system so we can’t tell you without knowing the OS, Asterisk and FreePBX versions.
If you are using the distro you need to identify that, post in the right forum as the distro includes pre-configured span DSP and does not require Fax for Asterisk, in fact installing it will surely break the pre-configured faxing.