From manual switchboards and on-premises PBX hardware to VoIP and cloud communications, business telephony has changed dramatically over the past century. This series follows that evolution one technology at a time. After covering the PSTN, VoIP, SIP, SIP trunks, and DID numbers, we have reached the platform that brings many of those elements together. The next step is understanding what a hosted PBX is and how it brings many of these technologies together into a complete business phone system.