I have a hosted voip provider that states that their service is compatible with T.38.
I have a Grandstream HT802. (Actually 3, but I am trying to get one working before deciding whether to attempt the same on the other two.) The ATA is registered to the hosted provider, and set up to use T.38. The ATA has a fax machine connected to it. On some occasions the fax even completes a transmission without reporting communication errors - however that is by no means a majority outcome.
What am I doing wrong? If the answer is "not using a Cisco SPA112", I've heard it. I am considering that as a solution. However, I'd like to get some use out of the Grandstream hardware we purchased. IF anyone has managed to get this working in the UK and has some notes or config settings that might help, please reply.