Free IP PBXAsteriskAsterisk® is a complete IP PBX in software. It runs on a wide variety of operating systems including Linux, Mac OS X, OpenBSD, FreeBSD and Sun Solaris and provides all of the features you would expect from a PBX including many advanced features that are often associated with high end (and high cost) proprietary PBXs. Asterisk® supports Voice over IP in many protocols, and can interoperate with almost all standards-based telephony equipment using relatively inexpensive hardware.
Free PBXFreePBX is a Standardised Implementation of Asterisk that gives you a GUI to manage your system. If you’ve looked into Asterisk, you’d know that it doesn’t come with any ‘built in’ programming. You can’t plug a phone into it and make it work without editing configuration files, writing dialplans, and various messing about. FreePBX simplifies this by giving you a pre-written set of dialplans that allow you to have a fully functional PBX pretty much straight away.
TrixBoxtrixbox is a telephony application platform based on Asterisk™ Open Source PBX Software. The trixbox application platform makes it fast and simple to install and configure your business-class telephony system. With unlimited extensions, voicemail-to-email, music on hold, call parking, analog lines or high density T1/E1 circuits and many other features, trixbox provides all the functionality your business needs. trixbox brings big business PBX features to small and medium-sized businesses.
SipX - Free IP PBXsipX is the leading open source IP PBX in terms of scalability, robustness and ease of use. The sipX IP PBX has been successfully deployed in a lot of places. The largest known installation serves more than 5,000 users connected to one redundant (HA) system. Small installations go all the way down to a few users served by very low cost hardware.
