IP PBX

An IP PBX is a private branch exchange, or telephone switching system, that routes calls over an IP network for internal users and provides access to outside lines. Typically, an IP PBX also switches calls between VoIP users and callers on traditional telephone systems.

One main advantage of an IP PBX is that it eliminates the need for a separate voice network, instead converging voice and data traffic on the same network. The flexibility provided by one line for each user's data and voice access makes it easier for enterprises to add users and can reduce long-term operational and maintenance costs.

IP PBXes, which are usually software packages running on a server or dedicated appliances, have a variety of features for managing calls. Some of them are voice-menu systems, call conferencing, click-to-call, call logging and tracking, voice mail and call forwarding.

Companies can decide to use softphones, software-only implementations of IP phones that run on users' desktops, or traditional desktop phone sets that have been designed to work over IP networks. Proprietary IP phones made by the same vendor that makes an IP PBX limit interoperability but can also take advantage of the PBX's features to a greater degree than standards-based IP phones.

Additional resources

IP PBX Software Buyer's Guide

Network World IP PBX Research Center.