Short for Private Branch Exchange,PBX is a private telephone network used within an enterprise.
Users of the PBX share a certain number of outside lines for making telephone calls external to the PBX.
Most medium-sized and larger companies use a PBX because it's much
less expensive than connecting an external telephone line to every
telephone in the organization. In addition, it's easier to call
someone within a PBX because the number you need to dial is typically
just 3 or 4 digits.
A new variation on the PBX theme is the centrex,
which is a PBX with all switching occurring at a local telephone
office instead of at the company's premises.
