Freepbx

Web-based open source GUI that controls and manages Asterisk.

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Scalable open source cross-platform telephony platform.

Easy to use but advanced IP PBX system, VoIP gateway and conference server.

Modular SIP server (registrar/proxy/router/etc).

Troubleshooting and monitoring VoIP calls.

Lightweight SIP proxy, location server, and registrar for a reliable and scalable SIP infrastructure.

SIP proxy/server for voice, video, IM, presence and any other SIP extensions.