3CX Phone System is a specialist, Debian-based Linux distribution designed to run a complete unified communications platform. The 3CX client, included in the distribution, can also be installed separately on most hardware as well as the cloud. It provides a complete open standards-based IP PBX and phone system that works with popular SIP trunks and IP phones. It will automatically configure all supported peripherals and it also comes with clients for Windows, OS X, iOS and Android. The ISO image includes a free license for the 3CX PBX edition. The ISO image contains the standard Debian installer which installs a minimal system with the nginx web server, PostgreSQL database, iptables firewall and Secure Shell. Options not relevant to 3CX have been removed from the distribution.