[Asterisk-Users] Digium cards, so disappointing !

[Remco Barende]

On Sat, 15 Apr 2006, Kevin P. Fleming wrote:

> Actually, I did. During a FAX transmission, there are many shifts to
> different carriers and signaling rates as pages are transmitted and
> acknowledged. It is _not_ as simple as a single carrier, like a normal
> data modem connection. In addition to those shifts occurring, they are
> very strictly timed and must occur within fairly short windows.

Hi Kevin,

I think the biggest problem is that almost any more modern fax machine 
persistently tries to connect at the highest possible speed.

To solve the problem I suggested a workaround to this earlier on the list, 
no idea if it is technically possible or dfficult to implement, this is 
what I wrote :

record the sound fax machines make when negotiating (specifically the part 
where they try to negotiate anything above
9600 baud) and make a provision in asterisk (an extra letter added to the 
Dial command?) that will make Asterisk monitor
the channel and listen for the fax nego sounds and have Asterisk distort 
or mute the audio. This way all fax machines
would be forced to lower their speeds.

I suspect that such a solution would greatly improve reliability for 
faxing without the need for drastic changes in the
way asterisk works. If you could lower the speed further down to 4800 or 
even 2400 baud that might even be an interesting
option. Instead of faxing at 9600 or 14k4 through a normal (expensive) 
landline it could be cheaper to fax even at 2400 baud
via a voip line depending on where you need to fax to.

None of my fax machines are able to reduce their TX/RX speeds, if any 
devices capable of capping the speed it would be a
nice addition to the wiki, I would instantly buy some all-in-one machines 
that could do that


The lower connection speeds wouldn't bother me, reliable faxing would make 
up for the lost connection speed!