A PRIVATE BRANCH EXCHANGE (PBX) PHONE SYSTEM is an internal telephony network that allows for inexpensive calls within a company or organization. It is an efficient form of unifying communications within an office or network of branches.
The PBX connects the private network to the Public Switched Telephone network (PSTN) for external calls. Specific outgoing lines are reserved for those calls.
Internet Protocol (IP) PBX is the newest development in the industry. This is the same system but uses VoIP and software to make communication more streamlined and less expensive.
Users of PBX systems have four options: PBX, IP PBX, Hosted/Virtual PBX, and Hosted/Virtual IP PBX.