PABX System

 

PBX is also referred to as PABX-Private Automatic Branch Exchange and EPABX-Electronic Private Automatic Branch Exchange.

 

PBXs are used to make connections amongst the internal telephones of a private organisation, which are usually business oriented. They are also connected to a public switched telephone network (PSTN) through trunk lines. As they incorporate telephones, modems, fax machines, and many more parts, the general term "extensions" that is given is referred to the end point on the branch.

PABXs are differentiated from the key systems in which the users of the key system manually select the outgoing lines, whereas the PABX phone system selects it automatically. There are some hybrid systems that combine both the features. In the beginning, the main advantage of PBXs was the cost saved on internal phone calls, handling the circuit switching and thus locally reduced charges for the local phone service. Over the time, as PBXs increased in their popularity, it started offering many more services than the operator network, like call forwarding, extension dialling and hunt groups. In the early 1960s, there was a simulated PBX known as Centrex, which provided many similar features as the central telephone exchange.