t38 Fax for Asterisk 10, 11

I am using FreePBX distro 2.210.62-7
I want to send a fax from one fax machine to another via VoIP. It is my understanding that Asterisk 10 & 11 both support T.38 gateway mode so there is no reason why this should not work (yet I can’t get it to work). I don’t wan’t fax to email or email to fax. I want a true pots line solution where we can connect a real fax machine to the voip adapter and send a fax to another fax machine.

I don’t mind paying for an answer (support or community). I also looked at fax pro module but it doesn’t do what I want.

Does anyone have an answer?

FreePBX has no support for gateway mode by default but I am pretty sure its in Fax Pro for FreePBX 2.11 as we use it at Schmooze

Thanks. If you are sure I’ll buy the module. Is it tied down to one system? Can I transfer a paid module from one system to another?

Yes I am positive its in 2.11 as I just checked and I just put in a request to document department to update the sales information.

Yes all commercial modules are tied to a specific install and as stated in ToS you can move a module to a new system twice from our portal.

$250 is well worth it for a reliable faxing solution. I checked the sales information and the user guide regarding the T38 gateway option and while gateway mode is mentioned in the sales info there is nothing in the user guide. Can you ask them to add a section about gateway mode? I am ready to buy.

Its already in progress to get updated. Not sure when that will be. Its 2 real basic settings.



Got it. Thanks. If this works it’s amazing. Connecting a standard fax machine to Asterisk has been on my “to do” list for years now. I know everyone says fax is obsolete but in reality everyone still uses it once in a while. Do you recommend Asterisk 10 or 11 for this?

We dont get into recommending Asterisk versions. We use 10 on our fax server that we have this running on.

As I stated in my first comment on this thread.

FreePBX has no support for gateway mode by default but I am pretty sure its in Fax Pro for FreePBX 2.11 as we use it at Schmooze

I purchased the module. (
I am running FreePBX distro 2.210.62-7-
I did service httpd restart
I can see some of the fax pro fields in fax settings and extension BUT the
T38gateway option does not exist anywhere in the system.
Maybe those fields are added in a future version?

It’s working with 2.11 but not as intended. Maybe my settings are wrong. Please correct. I got a fax machine connected to my ATA and my other fax is connected to the PSTN.

On the ATA side T.38 is enabled (auto-detect)
On the Asterisk side
chan_dahdi.conf faxdetect=both
The extension is T38 gateway
and the outbound route is also T38 gateway
My asterisk sip settings are "T38 pass-through = yes"
My udptl.conf file has ports 4000-4999 open and my firewall too. (I even tried with my firewall off)

When I send a fax only page 1 goes through at 2400bps
When I set asterisk sip settings to "T38 pass-through = no"
all 3 pages go through much faster but "fax show sessions = 0"
which means it’s not using t38 mode but g711 pass-through.

What am I doing wrong? Which settings am I missing? This should work.

FAX For Asterisk Components:
Applications: 10.12.1
Spandsp FAX Driver: 20090502 044449

FAX For Asterisk Settings:
ECM: Enabled
Status Events: Off
Minimum Bit Rate: 14400
Maximum Bit Rate: 14400
Modem Modulations Allowed: V17,V27,V29
FAX Technology Modules:
Spandsp (Spandsp FAX Driver) Settings:

FAX show capabilities
Registered FAX Technology Modules:
Type : Spandsp
Description : Spandsp FAX Driver
Capabilities : SEND RECEIVE T.38 G.711 GATEWAY
1 registered modules

FAX Session Details:

session : 4
operation : Gateway
state : Active
ECM Mode : No
Data Rate : 2400
Page Number : 1