Private Analogue Branch Exchange. Older switches used an analogue form of operation, however these have (mostly) been superseded by digital types, known as PBX (private Branch Exchange) or PDBX (Private Digital Branch Exchange).
Private Automatic Branch Exchange
Private Automatic Branch Exchange- typically the private exchange associated with a business. Also called a PBX Private Branch Exchange.
Private Automated Branch Exchange
Private Automatic Branch Exchange
Private Automatic Branch Exchange. See PBX