An IP PBX is a private branch exchange that switches calls between VoIP (voice over Internet Protocol or IP) users on local lines while allowing all users to share a certain number of external phone lines. The typical IP PBX can also switch calls between a VoIP user and a traditional telephone user, or between two traditional telephone users in the same way that a conventional PBX does
We use Asterisk as our main Software to run all our IP-PBX's. It is a versatile and stable system that will meet all of your needs.