multiple instances of pbxnsip in a multi-tenant mode allowing them to offer Cloud based or "hosted" solutions to businesses. Security The PBX has a special focus on security. It was one of the first SIP PBX systems that supported the Secure Real-time Transport Protocol and seems to be robust against forms of Denial of Service, for example the INVITE of Death. Configuration There is a graphical user interface (GUI) for pbxnsip which allows administrators to view, edit, and change various aspects of pbxnsip via a web interface. Regional versions While initially developed in the United States, pbxnsip has become a popular VOIP PBX worldwide due to its design, extensibility, and excellent feature set. As a result, the American-English female voice prompts for the Interactive voice response and voice mail features of the system have been re-recorded and made available in Danish, Dutch, Spanish, Italian, German, Polish, Greek, French (Both Canadian and French dialects), Swedish, Russian, Brazilian Portuguese, British English, and Turkish. See also Voice modem Comparison of VoIP software List of SIP software IP PBX VoIP References External links pbxnsip wiki pbxnsip user forum Telephone exchanges Communication software