PBXs

PBX stands for Private Branch Exchange, a private telephone switching system within an organization. A PBX connects internal telephones within the organization and routes calls to external networks via trunks to the PSTN or via IP networks for VoIP.

Traditional PBX systems are hardware-based, located on premises, and use analog or digital trunk lines. IP-PBX systems use Internet Protocol to carry voice traffic and often run on standard servers, enabling integration with data networks and other communications applications. A growing variant is hosted or cloud PBX, where the PBX functionality is provided by a service provider over the Internet and accessed by the organization’s phones.

Key components include the PBX processor or server, telephony interfaces or gateways, endpoints such as desk phones or soft clients, voicemail and auto-attendant, and management software.

Common features cover internal extension dialing, call routing and trunk access, voicemail with greeting and transcription, call forwarding, call hold and transfer, conferences, IVR menus, call queues, and presence-aware routing.

Deployment considerations include capacity planning for simultaneous calls, scalability, redundancy, security, and maintenance costs. Hosted PBX can reduce on-site hardware but relies on network reliability and vendor availability. In modern environments, IP-PBX and hosted PBX solutions support mobility, integration with collaboration tools, and unified communications, while preserving the traditional role of connecting internal users to the external telephone network.