Fax device does not send/receive with HT802

[Chili.]

Hello,

the constellation is this:
3cx Server (Self hosted - cloud) <-- SBC <-- Grandstream HT802 <-- fax device (Brother 8360p)

troubles:

• Sending and receiving with the fax device is not possible to other fax devices
• Sending and receiving with the fax device is possible to other devices using t.38 protocol

information:

• Baud rate can't be changed on the fax device
• Passthrough protocol is selected
• HT802 is provisioned with "fax" extension - I can hear the fax signal by dialing the DID number
• HT802 has the newest firmware
• fax extension has g711 codec selected

Can anyone help me? I also tried this configurations:

• https://www.3cx.com/voip-gateways/grandstream-ht-fxs/
• https://helpdesk.t38fax.com/hc/en-u...e: Fixed,Disable Network Echo Suppressor: Yes

 

[Evolute IT]

Does the SIP provider supports T38 or G711 Fallback for fax?

 

[Chili.]

Does the SIP provider supports T38 or G711 Fallback for fax?

yes, both

 

[Evolute IT]

yes, both

Then you should be configuring the HT and 3CX has T38 and not G711 Fallback.

Also, make sure the config is persistent across the flow (from provider to device.)

Last thing would be to reset the HT, then provision it again using the fax extension to make sure that there's no remnants of old config. You can also try using a real extension for testing.

 

[Chili.]

Then you should be configuring the HT and 3CX has T38 and not G711 Fallback.

Also, make sure the config is persistent across the flow (from provider to device.)

Last thing would be to reset the HT, then provision it again using the fax extension to make sure that there's no remnants of old config. You can also try using a real extension for testing

what do you mean by "a real extension"?

I used a "fax" Extension and the Inbound rule with "send to fax"

 

[Evolute IT]

Fax extension is usually fine. What I mean by real one is to use one from the Users section.