Digium Analog gateway inbound faxes received from allworx pbx (over sip) fail

T.38 fax is not supported on Allworx- 6X, 6X12, 24X, 48X 
G.711 fax is supported.

To Enable G.711 or audio passthrough as it is referenced on the Digium analog gateway series you must enable audio passthrough on the analog gateway following the directions below.

On the gateway select the following:

• Configuration

• SIP Endpoints

​Within Sip endpoint click the modify button beside the SIP Endpoint created for the Allworx PBX.
Choose the fax settings tab.

Note: Enable Advanced Options must be set to yes in order to access the fax settings tab.

Set Fax Mode to Audio Passthrough and select Save Endpoint.