This blog post will explain what a SIP enabled PBX is. SIP stands for session initiation protocol. It is a private branch exchange system that handles incoming and outgoing calls over public and private networks using SIP trunking. An SIP trunk uses the VoIP protocol to send outgoing calls and receive incoming calls. That is also known a SIP termination and origination. SIP enabled PBXs connect to the Internet instead of PRI lines provided by a PSTN provider. SIP trunking is a more cost effective solution than PRI lines. It is a one of a few standards that allow SIP devices to talk to each other over a public or private network. Most services provided by SIP trunking have a good chance of being compatible with an existing PBX. Several concurrent calls and direct dial numbers can be supported by SIP trunking. Inbound routes can be setup in a PBX to ring extensions or ring groups. There is no need for a receptionist to answer and transfer calls. SIP trunking has included benefits such as call statistics, disaster prevention, and a more effective way to route calls. SIP trunking replaces PSTN phone lines with direct dial numbers. The virtual connection to the PSTN is handled by the internet telephony service provider. A SIP enabled private branch exchange can be hardware or software. Besides voice communications, SIP trunking supports video conferencing and other types of multimedia sessions. Things to consider when buying a new private branch exchange is access to a good Internet connection, a private branch exchange that works with the SIP protocol, and choosing a internet telephony service provider that compatible with a companies private branch exchange system. Hosted PBXs or cloud PBXs are hosted by a third party cloud provider. Virtual PBXs are ran through VirtualBox or VMWare virtual machines. Legacy PBXs use the PSTN for connectivity.