Asterisk - An open source telephony switching and private branch exchange service for Linux.
Freshcaller - Freshcaller is a modern-day reimagining of our everyday phone system for customer support, sales, IT, and HR teams.
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.
NICE inContact - Get the DMG Consulting report reprint on cloud contact centers.
FusionPBX - FusionPBX is an open source FreeSWITCH GUI.
Bitrix24 - Bitrix24 is a free (for small businesses) social enterprise platform. It is a united work space which handles the many aspects of daily operations and tasks. Create your own social intranet in minutes!