Telephony Systems and VoIP
PBX stands for Private Branch Exchange, which is a private telephone network used within a company. The users of the PBX phone system share a number of outside lines for making external phone calls.
A PBX connects the internal telephones within a business and also connects them to the public switched telephone network (PSTN).
One of the latest tendencies in PBX phone system development is the VoIP PBX, also known as IP PBX, which uses the Internet Protocol to transmit calls, rather than the public switched telephone network (PSTN). The steps involved in originating a VoIP telephone call are signaling and media channel setup, digitization of the analog voice signal, encoding, packetization, and transmission as Internet Protocol (IP) packets over a packet-switched network.