What is PRIVATE BRANCH EXCHANGE? What does PRIVATE BRANCH EXCHANGE mean? PRIVATE BRANCH EXCHANGE meaning - PRIVATE BRANCH EXCHANGE definition - PRIVATE BRANCH EXCHANGE explanation.
Source: Wikipedia.org article, adapted under https://creativecommons.org/licenses/by-sa/3.0/ license.
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A private branch exchange (PBX) is a telephone exchange or switching system that serves a private organization and performs concentration of central office lines or trunks and provides intercommunication between a large number of telephone stations in the organization. The central office lines provide connections to the public switched telephone network and the concentration aspect of a PBX permits the shared use of these lines between all stations in the organization. The intercommunication aspect allows two or more stations to directly connect while not using the public switched telephone network.
Each PBX-connected station, such as a telephone set, a fax machine, or a computer modem, is often referred to as an extension and has a designated extension telephone number that may or may not be mapped automatically to the numbering plan of the central office and the telephone number block allocated to the PBX.
Initially, PBX systems offered the primary advantage of cost savings for internal phone calls: handling the circuit switching locally reduced charges for telephone service via central-office lines. As PBX systems gained popularity, they began to feature services not available in the public network, such as hunt groups, call forwarding, and extension dialing. From the 1960s a simulated PBX known as Centrex provided similar features from the central telephone exchange.
A PBX differs from a key telephone system (KTS) in that users of a key system manually select their own outgoing lines on special telephone sets that control buttons for this purpose, while PBXs select the outgoing line automatically, or formerly, by an operator. The telephone sets connected to a PBX do not normally have special keys for central-office line control, but it is not uncommon for key systems to be connected to a PBX to extend its services.
A PBX, in contrast to a key system, employs an organizational numbering plan for its stations. In addition, a dial plan determines whether additional digit sequences must be prefixed when dialing to obtain access to a central-office trunk. Modern number-analysis systems permit users to dial internal and external telephone numbers without special codes to distinguish the intended destination.
The term PBX originated when switchboard operators managed company switchboards manually using cord circuits. As automated electromechanical switches and later electronic switching systems gradually replaced the manual systems, the terms private automatic branch exchange (PABX) and private manual branch exchange (PMBX) differentiated them. Solid-state digital systems were sometimes referred to as electronic private automatic branch exchanges (EPABX). As of 2016, the term PBX is by far the most widely recognized. The abbreviation now applies to all types of complex, in-house telephony switching systems.
Two significant developments during the 1990s led to new types of PBX systems. One was the massive growth of data networks and increased public understanding of packet switching. Companies needed packet-switched networks for data, so using them for telephone calls proved tempting, and the availability of the Internet as a global delivery system made packet-switched communications even more attractive. These factors led to the development of the voice over IP PBX, or IP-PBX.
The other trend involved the idea of focusing on core competence. PBX services had always been hard to arrange for smaller companies, and many companies realized that handling their own telephony was not their core competence. These considerations gave rise to the concept of the hosted PBX. In wireline telephony, the original hosted PBX was the Centrex service provided by telcos since the 1960s; later competitive offerings evolved into the modern competitive local exchange carrier. In voice over IP, hosted solutions are easier to implement as the PBX may be located at and managed by any telephone service provider, connecting to the individual extensions via the Internet. The upstream provider no longer needs to run direct, local leased lines to the served premises....