PBX (Private Branch Exchange)

A private telephone switching system that connects internal extensions and routes calls to the public telephone network, increasingly IP-based (IP-PBX). Traditional PBXs used proprietary hardware and digital circuits; modern IP-PBXs (Asterisk, FreeSWITCH, 3CX) use SIP internally and connect to carriers via SIP trunks. Features include call routing, voicemail, IVR, conferencing, and call recording. Hosted cloud PBX solutions eliminate on-premises hardware entirely.