Aircall - Aircall is a call center software of a new generation designed for fast growing companies. Setup instantly and integrates to your CRMs
Asterisk - An open source telephony switching and private branch exchange service for Linux.
LeadMaster - The LeadMaster LeadMasterCRM All-in-One solution includes: marketing automation, lead management, email marketing, website integration & much more.
FreeSWITCH - FreeSWITCH is an open-source media application designed to support popular protools such as SIP and WebRTC and provides a platform to develop voice and video applications.
Servetel - Communication management solution
freepbx - FreePBX is a web-based open source GUI that controls and manages Asterisk (PBX).