3 - PBXs

Abstract

This chapter discusses private branch exchanges (PBXs). It also discusses the history, technical developments, and other characteristics of PBXs, and their use as local area networks. In a private branch exchange, intercommunicating calls within the organization are switched via switching equipment located on the organization's premises. Persons desiring to make calls to locations outside the company facility do so by dialing a prefix code that causes the PBX to select an available line to the telephone company exchange. In the case of a PBX, the operator advances the call through the PBX to the desired party, rather than alerting the desired party via a separate intercom. The dial access to outside lines and the call switching capability of the operator eliminate the need for outside lines to appear at each desk, permitting the use of an arbitrary number of outside lines. The technology used in PBXs has reflected that of their parents, the developments telephone company exchanges, although the technology used in small PBXs is sometimes more advanced than exchange technology.