During the 1990s, due to two significant developments, a new type of PBX system emerged. One is the rapid expansion of data networks and the widespread acceptance of packet switching by the public. Enterprise companies need data packet switching network. The prospect of using this network for telephone exchange is attractive. In addition, the wide use of the Internet as a global data switching system makes packet switching communication more attractive. All these factors contributed to the development of VoIP PBX.