[Asterisk-Users] Asterisk and HylaFax

[Lee Howard]

On 2004.12.17 05:42 Sergio Serrano wrote:
> Hi all,
>     again I try configure Hylafax with asterisk. I would like
> configure
> Asterisk in the next way:
>         1)An incoming fax go into through X100P
>         2)Asterisk detects Fax and redirect fax to Hylafax
> 
>     Is it possible?

Yes, but it may not be as pretty as you like, and it may not function 
as well as you hope.

Using faxdetect in your zapata.conf file will get practically all of 
the faxes coming in to the X100P routed to the "fax" extension.  The 
trick, then, is how to get HylaFAX at that fax extension.  There are a 
number of different ways to do it, but in each case, in the end, the 
idea is to get HylaFAX and Asterisk communicating at an Asterisk FXS 
point.  So you could do a number of different arrangements:

   X100P -> Asterisk -> SPA-2000 (ATA) -> Modem -> HylaFAX

or

   X100P -> Asterisk -> TDM400P (FXS) -> Modem -> HylaFAX

but, at that point you probably would be better off without the X100P 
like this:

   TDM400P (FXO) -> Asterisk -> TDM400P (FXS) -> Modem -> HylaFAX

I will warn you now, however, that the analog-to-digital and then 
digital-to-analog conversions that are required in these arrangements 
seem to cause some problems.  You may never notice the problems if you 
use ECM on the receiving modem, but if you pay attention to the ECM 
logging, you may notice that you'll get more data corruption (and thus 
retransmissions of data) than you would if you just had the modem 
plugged into the POTS line directly.  I don't know if that's an error 
on the part of Asterisk, or on the part of all of the ATAs that I've 
heard mentioned used in this situation.  In fact, I've even heard of 
that same problem when using a TDM card instead of the ATA.  Maybe it's 
just an inherent problem with the A->D & D->A conversions.  I don't 
know.

In any case, currently the best way (the way without any data 
corruption as I mention) to interface Asterisk and HylaFAX is to keep 
everything digital...

   TE405P -> Asterisk -> TE405P -> T1 Modem (Patton 2977) -> HylaFAX

But this requires more expensive hardware and more expensive lines and 
is probably beyond the scope of your project since you're talking about 
faxdetect and X100Ps.

There are some "futuristic" arrangements that could be done conceivably 
with some tools that are available, such as spandsp or t38modem, but 
currently there is no way to interface t38modem with Asterisk and no 
way to interface spandsp directly with HylaFAX.

Lee.