The 3CX Phone System is the software-based private branch exchange (PBX) Phone system based on the SIP (Session Initiation Protocol) standard and enables extensions to make calls via the public switched telephone network (PSTN) or via Voice over Internet Protocol (VoIP) services...
FreePBX is a web-based open source GUI (graphical user interface) that controls and manages Asterisk (PBX), an open source communication server. FreePBX is licensed under the GNU General Public License (GPL), an open source license.
PBXware is the world’s first and most mature IP PBX Professional Open Standards Turnkey Telephony Platform. Bicom Systems’ softswitch is offered in the Business, Call Center and Multi-Tenant Editions.