[asterisk-users] setup for fax machine

Andrew Joakimsen
Sun, 12 Oct 2008 22:09:38 -0000

On Sun, Oct 12, 2008 at 5:17 PM, sean darcy <seandarcy2 at gmail.com>
wrote:
> Becasue of all the issues with fax over voip, we want to use pstn for
> our fax machine, but not dedicate a line just to fax.
>
> I'm thinking of having asterisk answer the pstn line, check for fax
> tones, and route appropriately. In zapata ( chan_dahdi ) set
> faxdetect=incoming
>
> then the dial plan would have
>
> [incoming-pstn]
> exten => fax,1,Dial(DAHDI/1)  ; the fax machine
> exten => fax,2,Hangup()
>
> exten => s,1,Answer()
> exten => s,2,Dial(DAHDI/2)   ; internal extension
> .............
>
> Would this work? I'll need another TDM410 card to do this, so I'd
like
> some reassurance before I go purchase it.
>

Another thing you can do is get a "comswitch" -- they are pretty cheap
and have been around for years.
http://www.commandcommunications.com/products.php IMO they work pretty
well.

I use these as a backup. I use VoIP "only" at some sites and the fax
line is used for the DSL. The comswitch is connected to the line and
then connect the asterisk machine (using a cheap "winmodem"), fax
machine and a red WECo 2500 clone. So if the DSL goes down the calls
get routed through that phone line and the comswitch routes them to
the Asterisk machine and the IP phones ring like normal. If the PBX
goes down or the power for a long time, they can use the "Red phone"

The main motivation for going to this setup was a low cost way to keep
911 working while trying to stay 100% voip . The comswitch was
installed so in case 911 needs to call back it won't go straight to
the fax. The use of the line as a backup ended up being an unintended
consequence, but it seems to work well.

This setup works very well, but if you are using this on a "main"
phone line then be advised there will be an extra 1-2 ring delay --
the comswitch actually answers the call when it comes it and does fax
detection. I also see these installed in many retail stores --
normally they will have 3 lines in a hunt group -- the 3rd line is
shared between the fax and the hunt group using the comswitch.