A private branch exchange (PBX) is a telephone exchange that serves a particular business or office, as opposed to one that a common carrier or telephone company operates for many businesses or for the general public. PBXs are also referred to as PABX – private automatic branch exchange and EPABX.
The electronic private automatic branch exchange (EPABX) is equipment that has made day-to-day working in the offices much simpler, especially in the area of communication. The EPABX may be defined as a switching system that makes available both internal and external switching functions of any organization.