A telephone exchange, also called PBX (Private Branch Exchange, private switching Branch), is a private telephone exchange that usually belongs to a company, which allows to make connections among the internal telephones as well as connect them to the PSTN (switched Telefonica network) via trunk lines. Basically, a switchboard can be PBX or IP PBX, can be in both cases a Centrex switchboard emulation service contract with the telephone company. Features a telephone switchboard or PBX is a private automatic switch that normally attends an Office, private organization or a business, enabling interconnect handsets internal in addition to managing phone calls through trunk lines of public telephone companies. Usually uses the generic term extension to refer to any internal telephone device, such as telephones, fax machines, or modems. The switchboard is a basic component in the communications infrastructure of a company. Currently the telephone switchboard PBX is no longer limited to large companies team and is used increasingly in medium-sized and small enterprises and in many homes.
Types there are basically two types of telephone switchboard or PBX: PBX: is a telephone exchange directly connected to the public telephone network PSTN via trunk lines that manages autonomously internal calls both the external (incoming and outgoing). It generally belongs to the company that has it installed and not to the telephone company. IP PBX (also called VoIP PBX): an IP switchboard is a telephone equipment designed to provide communication services over data networks via the Internet, using VoIP technology (Voice over IP, voice over IP). Currently most PBX have functionality IP PBX, allowing to operate both through data networks via RTC. Virtual PBX Telephone companies offer simulated service PBX, which consists of the public telephone exchange of the zone is configured in such way that lines that arrive to the customer appear to function as a telephone PBX switchboard, providing each extension of a pair of wires that connects to the telephone company central.
Therefore, the telephone company owns and manages all the communications equipment and software required to deploy the service, and no switching equipment located at the customer premises, to which the service is provided only. Sometimes operators offer this service under the telephone number only or similar designation. There is the possibility to contract with the telephone company a telephone switchboard PBX or IP PBX emulation service: Centrex (also called Virtual PBX or Hosted PBX): equivalent to a telephone switchboard PBX service. The term Centrex comes from Central exchange (clearing house). IP Centrex (also called Virtual IP PBX or Hosted IP PBX): functionally equivalent to an IP PBX switchboard.