[Asterisk-Users] faxing

[Lee Howard]

On 2004.07.28 19:33 matthew at txlink.net wrote:
> What are your experiences with faxing through Asterisk to the PSTN?

I have a setup that goes like this:

PSTN <--> X100P <--> Asterisk <-uLAW-> SPA-2000 <--> HylaFAX 4.2.0

Asterisk reliably detects and routes incoming faxes to the appropriate 
station (one-line setup).  I had to adjust some of the timings 
(lengthening them) in the HylaFAX modem configuration file, but other 
than that I have had no problem sending and receiving domestic faxes 
this way.  I use ECM, so it compensates for most of the problems that 
can arise, but I do notice more difficulty in getting the fax through 
than when the HylaFAX modem is connected directly to the PSTN.  
However, I tried an international fax the other day, and it did not go 
through.  I had to take Asterisk out of the loop.

I am anxiously awaiting (and looking to help develop) Steve Underwood's 
(spandsp) pseudo-tty Class 1 modem for Asterisk.

> We are using g.711u as a codec, and are originating/terminating with
> Broadvox as
> well as through our own PSTN gateways.

You really must use a lossless codec, so g.711u (uLAW) is appropriate.  
However, you'll still probably have more success going through the 
local PSTN than through a VoIP carrier.

> We have had some luck with incoming faxes coming into our network from
> Broadvox
> DIDs.  They work 50% of the time.  Not sure yet on PSTN incoming since
> nobody
> that is using FAX is in our local rate centers.
> 
> Outgoing has been bad.  It seems to work the best if the Sipura user
> agents have
> echo cancelation off,

You must have echo cancellation off on that station.

> but we have to have echo cancelation on our
> outbound
> gateways or there is echo in the voice path.  Faxing outbound works
> very
> rarely, and if it does, it usually can only send a page or two before
> we get
> the infamous "Poor line condition".
> 
> Does anyone have a suitable FAX setup working?

I tend to believe that there are lots of us.

That said, I think that doing it the old-fashioned way may be better 
for the time-being.  So if you have dedicated fax lines, just run them 
directly to the fax device rather than through a PBX.

Lee.