VoIP Basics: How Business Phone Systems Work

VoIP (Voice over Internet Protocol) converts voice calls into digital data packets transmitted over IP networks — the same infrastructure as your internet connection. Unlike traditional PSTN (Public Switched Telephone Network) phone lines, VoIP requires no dedicated phone wiring and can be managed entirely through software. Key components: an IP PBX (Private Branch Exchange) or hosted VoIP platform manages call routing, voicemail, and features. SIP (Session Initiation Protocol) is the most common signaling protocol — it sets up, maintains, and terminates calls. RTP (Real-Time Protocol) carries the actual audio stream. SIP trunks connect the business phone system to the public telephone network through an ITSP (Internet Telephony Service Provider). Hosted VoIP (cloud PBX) means the PBX lives in the provider's data center — common providers include RingCentral, 8x8, and Vonage. On-premises PBX (e.g., 3CX) runs on a local server or VM that you manage. Hybrid models combine both. Hosted is generally preferable for small businesses due to lower upfront costs and managed maintenance.