At the moment we are testing 3CX. Now I am searching for the hardware to get the ISDN lines converted to VOIP. I have had a look at the hardware list on the website. There is only the Patton device which supports 4 ISDN ports (8 lines). But it seems to be hard to find it in the EU. The AVM VoIP Gateway 5188 looks interesting. It would be easy to replace in case the hardware fails. Does anybody know if this gateway does the job?