What is PBX (Private Branch Exchange)?
A PBX (private branch exchange) is the system that routes calls inside an organisation and connects it to the outside telephone network, so staff share a set of external lines rather than each having their own.
Historically a PBX was a physical cabinet on the premises, wired to every desk. It handled extensions, transfers, hold and voicemail, and its capacity was fixed by the hardware installed.
A cloud or hosted PBX does the same job from the provider's infrastructure. Extensions become software registrations rather than wired ports, so a handset, a laptop app and a mobile can all be the same extension.
The decision between them is rarely about features any more — it is about who carries the operational burden. An on-premise PBX means owning capacity planning, patching, power and failover. A hosted one moves that to the provider and makes it a subscription.
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