Architecture

VoIP vs PBX (and the difference)

VoIP and PBX are often used interchangeably but mean different things. VoIP is the transport layer (calls over IP). PBX is the application layer (call control, extensions, IVR, recording). Most modern systems combine both, but they are distinct concepts.

Side-by-side

	VoIP	PBX
What it is	Protocol layer (SIP+RTP) that carries voice over IP networks	Application that routes/controls calls inside an organization
Examples	SIP, H.323, WebRTC	Asterisk/FreePBX, 3CX, RingCentral, Teams Phone
Layer	Transport / signaling	Application / business logic

Possible combinations

• VoIP without PBX: a softphone or AI voice agent calling a SIP trunk directly — no internal extensions or IVR.
• PBX without VoIP: a 1990s analog PBX with copper-wire trunks — legacy, mostly extinct.
• VoIP + PBX (most common today): an IP-PBX (FreePBX, 3CX, Teams) speaking SIP to upstream carriers and to internal endpoints.

In short

If someone asks 'should I get VoIP or a PBX?' the answer is usually 'both' — you want a modern IP-PBX (or hosted/cloud PBX) connected via VoIP (SIP trunks) to a carrier like DIDHub.

Related terms