[Asterisk-Users] Sending faxes and call accounting

[Rich Adamson]

> >I don't understand you're confidentiality arguement. If asterisk is
> switching the call, it /can/ save a copy of the transmission.
> 
> Of course, we know that. But the perception is that the fax machine is
> private, so that's what the clients want.
> 
> >None the less, you should be able to switch a fax call just like a voice
> call.
> That's not what I am reading, but I will set up a test.
> I would like to run hylafax for another installation, my own office, but I
> am not clear on how this is achieved. I already run hylafax on another
> machine, but what I cannot figure is, if I run it on Asterisk do I need the
> modem, or does it receive on the FXO port the line is connected to?

You sort of have to read between the lines in the archives.

Switching fax calls that arrive via digium TDM-fxo ports will not work
in the majority of cases. There are apparently a few exceptions, but
most users of that card have an issue with internal bus problems that
end up as missed frames, etc. Fax/modem calls will fail in those cases.
That includes the use of spandsp. Probably less then a 10% chance of 
making that work reliably.

Switching fax calls that arrive via T1/E1's is far more reliable, however
one must use the g711 codec (ulaw or alaw), AND, some fxs adapters
work well while others don't. Probably greater then a 90% chance of
making that work "if" you spend some time researching sip-fxs adapters.

Using external sip-fxo boxes (such as the Sipura spa-3000) has had
mixed results. Some are capable of recognizing fax tones while others
don't handle that well at all. However, using an external sip-fxo
box essentially dictates dedicated pstn analog fax lines. The
probability of success will be highly dependent on the sip-fxo box.

In each case mentioned, any missed/dropped frames regardless of the
root cause (eg, overloaded or poorly configured * box, poor network 
infrastructure) will negatively impact fax and modem operation. That
includes your guest's use of laptops and analog modems as well.

The hylafax approach requires a dedicated analog pstn line and analog
modem in all cases that I'm familiar with. Once the fax arrives
successfully, you still have the issue of how to deliver the *.tiff
(or whatever format) file to your guest (and confidentiality concerns). 
Others may be able to address whether hylafax can support isdn 
interfaces, etc. I don't have a clue.

In the archives you'll see several posts where * users have been
able to make fax's work. Keep in mind while reading those that a
fair number of posts are coming from people with small soho
implementations, and their definition of "reliable" in that
low volume environment will very likely be different then your 
definition.

Bottom line: faxing over voip systems tends to be problematic and
requires a significant amount of testing in "your" environment.