Glossary definition of Private Automatic Branch Exchange

Also known as: PABX

Private Automatic Branch Exchange (PABX) is the type of telephone exchange often found in offices and companies, which have automated switchboards and possibly hundreds of extensions.

A PABX performs all the switching necessary for making internal calls between extensions within the organisation, and it also enables the connection between extensions and the external phone lines operated by the local network carrier. In practice, most private branch exchanges (PBX) are now automatic, and the operator or receptionist is usually only needed to provide information and manual connections for outsiders who are unfamiliar with the company.

The exchange is called 'private' because it is owned and operated by the private organisation in which it is installed, and it is called 'automatic' because it relies on electronic or computerised control equipment to handle the switching of the calls, rather than the use of a human operator.