EPBXs make connections among the internal telephones of a private organization usually a business and also connect them to the public switched telephone network, because they incorporate telephones, fax machines, modems, and more.
EPBX (Electronic Private Branch Exchange) : 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 PBX – private automatic branch exchange.
An IP PBX is a business telephone system designed to deliver voice or video over a data network and interoperate with the normal Public Switched Telephone Network. EPPBX is based on two technologies, VoIP and SIP.