A Private Branch Exchange (PBX) is a private telephone network used within a company.
It connects telephones within the organisation while sharing outside lines for making calls outside the organisation, so that each individual telephone user does not require a line directly to the telephone company.
Advantages of a PBX include cost savings for internal phone calls and the ability to feature services such as call forwarding and extension dialling.
PBX can be owned and operated by the organisation itself or hosted by the phone company.
PBX systems initially required a live operator to move the calls around, but this process can now be automated.
A growing category is IP PBX, which is a software-based version of the PBX. This uses Voice over IP technology to transmit calls.
PBX is generally used by medium and large companies as it is more economical, while the relative expense for small businesses may not be.