Free VOIP / SIP phone (softphone) for Windows. Works with popular VOIP providers and SIP PBX's (including Phone System, Asterisk and many more). The interface is easy to use and similar to that of popular Smartphones. is compact and easy to install across a network. Features include Call Transfer, Call Recording, Hold, Headset support, Call History.

Phone System for Windows is a software-based IP PBX that replaces a proprietary hardware PBX / PABX. IP PBX has been developed specifically for Microsoft Windows and is based on the SIP standard - making it easier to manage and allowing you to use any SIP phone (software or hardware). A software-based IP PBX / PABX offers numerous benefits:

Easier to install manage via web-based configuration interface
Far less expensive to purchase and expand than a hardware-based PBX / PABX
Improve productivity with presence, desktop based call control and extension management
No need for separate phone wiring - phones use computer network easy