Make the call and get it done with 3CS. 3CX Phone Systems are software-based IP PBXs that replace a proprietary hardware PBX. 3CX’s 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). When you want the best in business communication, 3CX by Decibel AVA is your match.