[Freeswitch-users] rxfax on b-leg

[Steve Underwood]

On 07/22/2011 12:56 AM, slash at nat-tele.com wrote:
>   Hello!
>
>
>   I wonder if there is a way to make rxfax recieve fax on outgoing call?
>   The idea is that registered FS user dials out, than tone_detect is used
>   to detect fax tone and start rxfax. The difference is that rxfax should
>   be run on B-leg, instead of A-leg in incoming fax call scenario.
>
>   I've tried to make a test config with outgoing call, rxfax&
>   tone_detect, but when I dial out and remote user starts sending fax to
>   me, FS detects a tone correctly, starts rxfax, but on my leg (A-leg, i
>   hear fax tones) and B-leg (with real fax machine) is hanged up.
>
>   Are there are solutions to explain somehow to rxfax that it should be
>   run on B-leg, not on A-leg?
>
>   Thanks in advance!
>
>   With best regards,
>   Kirill.
If you use rxfax at the outgoing end of a call, mod_spandsp expects to 
get that FAX by the polling procedure (i.e. the one you use when you 
dial into a FAX server to collect an information FAX from it). If you 
want to freely act as a simple FAX transmitter or receiver in the middle 
of a call, the current module code may not properly allow for that. As 
someone else said, there are tricks related to call transfers which can 
be used to coax the fax instance into caller or answerer mode. Spandsp 
does pretty much everything the FAX spec allows. If there is demand we 
could provide access to more of that functionality.

Steve