Private branch exchanges (PBXs) are private phone networks used within a company. PBX users share a pool of external lines to make external calls. PBXs are typically a piece of hardware that connects phones that in turn connect to the public switched telephone network (PSTN). With the evolution of IP telephony, PSTN phone system hardware has changed, but the main design has remained the same. Traditional PBX hardware is becoming obsolete.
PC Phone Systems
Vendors started to produce PC-based phone systems in the mid-1990s. Although many of these systems were based on Microsoft Windows NT, NexPATH created a UNIX-based phone system for small business use. These systems were less expensive and provided more features than PSTN systems, but they were based on the same circuit-switched architecture. A PBX is a mini-version of a phone company’s main office based on circuit-switched technology.
What Happened to Traditional PBX Systems?
Traditional PBXs are based on a distributed circuit-switched system. These systems replaced a central switch with a multitude of interconnected switches in either a bus interchassis or circuit-switched trunk line. With Voice over IP (VoIP), some systems began to morph into a hybrid circuit-switched–VoIP design that brought analog phones connected to a telecom hub and Ethernet Session Initiation Protocol phones together through an Ethernet switch connected to a WAN or Internet router to distribute calls to external sources through a WAN or the Internet.
With phone systems moving to IP-based telephony, changing work environments, a recession driving people to look for ways to cut costs, and several other factors, PBXs have been nearly phased out entirely. The quality of service, latency, jitter, and security issues that once plagued VoIP have mostly been resolved through advancing VoIP technology.
Traditional PBXs may be obsolete, but an IP PBX works off the same principle. An IP PBX switches calls between VoIP users while allowing each user to share a number of outside phone lines. IP PBXs can also switch and connect calls between VoIP users and traditional analog phone users or between two traditional phone users in the same manner that a traditional PBX can. One advantage to using an IP PBX is that it runs on converged data and voice networks. Internet connectivity, VoIP, and traditional phone communications can merge through a single line. As your business grows, you can reduce the long-term cost of maintaining a traditional PBX. As with a traditional PBX, the enterprise owns an IP PBX only, which costs less and is easier to maintain.
The future of PBXs may be grim, but the actual term will live on through IP PBXs. As more venders offer IP telephony solutions involving IP PBXs, traditional PBXs are becoming scarce, expensive, and more difficult to find support for. Although many predicted the death of PBXs more than a decade ago, they are still in existence and in use by some businesses. Businesses that still own and use a PBX either do not have the money to upgrade and rely solely on their existing PBX to run maintenance free or do not have the means to upgrade because of their IP architecture (or lack of). VoIP and other IP telephony systems will not linger forever, though: a new technology involving web browser–enabled phone and conference calling is still being developed. Web Real Time Communications (WebRTC) may become the next wave of Internet communications. A brief overview of WebRTC is available in How Will WebRTC Revolutionize VoIP Service?