asterisk users - Jan 2005 - External fax modem takeover of fxo?

Given all the issues with the fax DSP code and reliability, I'm looking
into the option of using an external fax modem instead of trying to
shoehorn asterisk into handling faxes properly...

I'm thinking of hooking up the faxmodem to the line directly, then
hooking the X100P to the modem's Phone port. 

Can I enable fax detection and use the fax extension to spawn an external
command (halafax) to receive the fax? In theory, this should cause the
modem to "take over" the line, disconnecting the X100P (causing a Red
alarm) and receive the fax.

What is the state of fax detection with the stable branch of * on an
X100P? Does it work reliably?

Do I need to wait() or will Dial still be able to detect faxes:

exten => s,1,Answer
exten => s,2,Dial(blah extension for phone|20|d)
exten => fax,1,System(tell-halafax-to-answer)

or is this required:

exten => s,1,Answer
exten => s,2,wait(5)
exten => s,3,Dial(blah extension for phone|20|d)
exten => fax,1,System(tell-halafax-to-answer)

Anyone doing something like this already?

On 2005.01.18 08:36 Walt Reed wrote:
> I'm thinking of hooking up the faxmodem to the line directly, then
> hooking the X100P to the modem's Phone port.
 From what I've been able to determine, Asterisk would be most unhappy 
if you did that.  On X100Ps that "phone" jack/port needs to simply be 
ignored.  I have a telephone connected to mine, but it's only there in 
the off-chance of an emergency, power outage, or to troubleshoot 
problems with the FXO.
> Can I enable fax detection and use the fax extension to spawn an
> external
> command (halafax) to receive the fax?
Uh, well, in the obvious way yes, but not in the way that you seem to 
be wanting to hear.

exten => s,1,Answer
exten => s,2,wait(5)
exten => s,3,....
exten => fax,1,Dial(FXS_PORT)

Where "FXS_PORT" is an FXS port where a HylaFAX-controlled modem is 
connected... or any other fax device for that matter.

The problem is, though, that there seems to be a significant amount of 
data loss when receiving with this configuration... even using ULAW.  
Now, an ECM-aware fax device may compensate well-enough, but there's 
still a problem.
> What is the state of fax detection with the stable branch of * on an
> X100P? Does it work reliably?
Fax detection is generally okay, but there are some problems.  See:

   http://bugs.digium.com/bug_view_page.php?bug_id=0002165

Lee.