Private branch exchange.
A telephone system operating within one building, company, etc. and having outside telephone lines.
(Private Branch eXchange) An inhouse telephone switching system that interconnects telephone extensions to each other as well as to the outside telephone network (PSTN). A PBX enables a single-line telephone set to gain access to one of a group of pooled (shared) trunks by dialing an 8 or 9 prefix. PBXs also include functions such as least cost routing for outside calls, call forwarding, conference calling and call accounting. Modern PBXs use all-digital methods for switching, but may support both analog and digital telephones and telephone lines. See IP PBX and WPBX.
A voice-optimized switching system physically located on the customer premises, serving the internal station-to-station communications requirements of one or more user organizations and with trunk circuits connecting to the public switched telephone network (PSTN) via one or more central office (CO) switches, and perhaps one or more other PBXs composing a private network.The term refers to the fact that the PBX originated as a switching system located on the subscriber's private premises and serving the subscriber's private communications requirements, while functioning as a branch (i.e., partition) of the public exchange. The first PBX was placed into service in the Old Soldiers' Home in Dayton, Ohio, in 1879. The first systems were non-standard modifications of CO switches. AT&T offered the first standard PBX, the No. 1 PBX, in 1902.The evolution of PBX technology can be organized along generational lines, as shown in Table P-1.
A type of internal telephone switchboard—typically circuit-switched networks—found in corporations. As telephony continues to evolve to Voice Over IP (or VoIP), companies will use a so-called “hybrid” networks made up of both circuit-switched and VoIP equipment. According to security experts, during this transitional period, present-day security vulnerabilities of circuit-switched networks will continue—including toll fraud, service theft, the use of unauthorized modems, and eavesdropping on the Public Switched Telephone Network—and new vulnerability issues will emerge. How security professionals deal with these vulnerabilities will depend on the selected vendor, the configuration used, and the particular deployment scenario under investigation. Collier, M. The Value of VoIP Security. [Online, July 6, 2004.] CMP Media LLC. Website. http://subscriber.acumeninfo.com/uploads2/5/E/5E9080CAB3A1ABE63E3B 8EFB7B21E22D/1090506012673/SOURCE/secureLogix.html.