We had the FF110 working ok on a 3COM NBX PBX. Now when the call comes in it doesn't appear to be sending the tones out for fax negotiation.
We found the problem to be the version they upgraded to on the 3COM NBX. It has a bug where it hangs up the port after 4 digits are sent. The problem version is 5.0.28. He downgraded back to 5.0.25 and now it is working properly again.