3CX VOIP Phone System FREE edition is a SIP-based IP PBX for Windows that eliminates phone wiring, enables hot desking & lowers call costs through VoIP providers. It's easy to install & configure, and eliminates vendor lock-in. Download FREE edition now.

One of the key features of 3CX Phone System is its web-based administration interface which makes phone system management incredibly easy. This software eliminates the need for a phone wiring network and allows users to hot desk by simply taking their phone.
3CX Phone System is a complete phone system that provides call switching, routing, and queueing. Furthermore, purchasing costs for this system are dramatically lower than those of a traditional hardware PBX. It's easily scalable, allowing you to add unlimited extensions and phone lines without the need for proprietary expansion modules.
The web-based configuration and status indication make phone system management a breeze, while unified messaging allows you to receive voice mail via email. An auto attendant feature lets callers choose from various options, such as "1" for sales and "2" for support. This system also helps you reduce long-distance and interoffice call costs, and there's no need to purchase expensive proprietary phones as you can use standard SIP phones.
By eliminating the phone wiring, you'll also make moving offices easier. And with its out-of-the-box configuration for many VoIP providers, 3CX Phone System is a no-brainer when it comes to implementing an effective office phone system.
Version 8.0:
All editions: revamped management console and user interface, run as a virtual instance in Hyper V, new configuration wizard, advanced call forwarding rules, supports Sangoma cards, optimized system performance
Commercial editions: advanced call queue rules, resolve inbound calls to Outlook
Version 5.1:
SIP forking
Tunnel to tunnel SIP traffic over a single TCP port
Ability to create outbound rules / dial plans based on number of digits. This allows a dial plan to be setup that does not require a prefix.
Extensions no longer need to be setup as internal or external - the PBX will rec
Version 3.0:
First implementation of support for external phone and gateway devices
Improved logging to show media stream parameters when call legs are created
Improved gateway/provider template handling including import facility
Improved support for extensions/providers/gateways by adding some advanced opt
Version 2.0: none