The 3CX Phone System is the software-based private branch exchange (PBX) Phone system developed by the company 3CX. The 3CX Phone System is based on the SIP (Session Initiation Protocol) standard and enables extensions to make calls via the public switched telephone network (PSTN) using Voice over Internet Protocol (VoIP) services.  VanBelkum deploys, manages, provides helpdesk, endpoint installation, networking & training for this software in the cloud for clients.