Hi, Creating a new thread. If it is any interest for a native stack in FreeSWITCH we could address it later. It lacks the state-engine. Actually, last time I asked I was told someone in Germany was working on this? But, as I looked at it recently I concluded that with Sangoma supporting their own boards, and Digium maintaining libpri for theirs - we basically have covered a majority of the E1/T1 boards that is used in here. Correct me if I am wrong. Jan <snip> Interesting. I've had more success with the libpri stack than the native stack because the native stack is definitely a work in progress. I assisted Mike J in getting 5ESS support in the native stack, but we definitely don't have explicit 4ESS support. I think you are better off using the libpri method and debugging it than trying to get the native PRI stack to work on a 4ESS connection </snip>