Stands for Private Branch Exchange, which is a private telephone network used
within a company or organization. The users of the PBX phone system can communicate internally (within their company) and externally (with the outside world),
using different communication channels like Voice over IP, ISDN, or analog. A PBX
also allows you to have more phones than physical phone lines (PTSN) and allows
free calls between users. Additionally, it provides features like transfer calls,
voicemail, call recording, interactive voice menus (IVRs), and call queues.
Traditional PBXs would have their own proprietary phones, such that there would be
a way to re-use these phones with a different system. This means that we either have
system-lock-in (we are bound to the same system because changing the system means
also changing phones, which makes it prohibitively expensive to break
away) or vendor-lock-in (we are bound to the same vendor because the
phones are only usable with systems from the same vendor, sometimes
only within a particular range of systems).
Time and technology, however, have changed the consumer telephony
landscape, with the flag-bearer being the Open-Standards-based IP
PBX. The point of the “IP” in this new era is that the phone calls are
delivered using the Internet Protocol as the underlying transport
technology. PBX phone systems are available as hosted or virtual
solutions and as on-premise solutions to be run on your own hardware.