FreePBX

Elastix is a unified communications server software that brings together IP PBX, email, IM, faxing and collaboration functionality. It has a Web interface and includes capabilities such as a call center software with predictive dialing.

Digium, Inc. is a communications technology company based in Huntsville, Alabama, and since 2018, a subsidiary of Sangoma Technologies Corporation. The company makes VoIP business phone systems, IP phones, and hardware products. It was founded in 1999 by Mark Spencer.