Small PBX System

This diagram shows a block diagram of a small PBX system. This diagram shows that a PBX system contains line interface cards that connect the PBX to outside communication lines (such as the PSTN). The PBX also contains station interface cards that adapt the PBX signals to the type of PBX extensions (PBX telephones) that are used with the system. The PBX unit contains a switch to interconnect stations to other stations or to outside lines. PBX call control software coordinates the overall operation of the PBX system. The PBX unit in this example has a data interface connection to allow a control terminal to setup and configure the settings of the PBX system. The PBX also has optional voice mail that connects some of the station interface lines to a voice mail storage system (e.g. a computer hard disk) that allows users to connect to the voice mail and play, transfer and delete stored audio messages. This example also shows that PBX systems may have backup power supplies to allow the PBX telephone system to continue to operate even when the primary power source is lost.