Receiving fax over sip extension

Asterisk Asterisk Support
1

Sir,

I am having running asterisk 1.4 system without any problem but now i want to receive fax over sip extension. So, which program i have to install and what change in extensions.conf to receive fax on sip extension.

Thanks

Rajeev.

2

SIP does not support fax. There is no program you can use to receive a fax over a SIP extension.

For more information, click here: http://www.soft-switch.org/foip.html

3

Sir,

Please tell me how to receive fax on sip extension.

Rajeev.

4

While this may certainly not be true in your case, I have been able to get fax working over SIP by using the ULAW codec. I also used NVFaxDetect to detect an incoming fax and dial the correct extension, you may not need that though if you have a dedicated number for fax.

Here is an example from my extensions.conf, using the NVFaxDetect mod.

exten => 2185551111,1,Answer
exten => 2185551111,2,NVFaxDetect()

exten => fax,1,Dial(SIP/fax_machine,40,tr)
exten => fax,2,Hangup

The line answers, NVFaxDetect checks to see if the incoming call is a fax, if so, it goes to the fax extension, where I dial my SIP DTA device that the fax machine is plugged into. I use Grandstream Handytone 268 units for this.

Here is the fax entry in my sip.conf

[fax_machine]
type=friend
context=fax_extension
username=fax
secret=password
host=192.168.0.78
nat=no
callerid=Fax
dtmfmode=RFC2833
disallow=all
allow=ulaw

Nothing special really, just forcing a higher quality codec and the fax detection (which may not even be necessary for you).

Otherwise it is pretty much luck of the draw, if it works for you, great, if not, too bad.

Also, the article posted above did an excellent job of describing the issue and why it happens.