I have a SIP Trunk that supports T.38. If I wanted to hook up a physical fax, could I get a FXS module to use for this. We only have 1 DID with the trunk. Or would I need an additional DID for faxing and then hook up the FXS module with fax to that DID?
yes, maybe you can test with sangoma analog card.
Easiest way is to get a T38 aware ATA (30 bucks for a SPA200? on ebay), in your inbound route set faxdetect On and choose SIP, redirect the fax call to that fxs extension.
rockbochs maybe a way to try!