RingCentral - RingCentral is the leading provider of cloud-based communications and collaboration solutions for small business and enterprise companies
Asterisk - An open source telephony switching and private branch exchange service for Linux.
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.
Twilio Video - Real-time video infrastructure and SDK
FusionPBX - FusionPBX is an open source FreeSWITCH GUI.
Truly Wireless - Wireless business phone system built for sales and support team.