This paper compares and contrasts the different traffic requirements of both voice and data communications. The role of evolving PBX technology in solving data communication needs is outlined, beginning with the analog PBX's of the 1970's and the digital-switching technology of the 1980's. The evolution of packet switching, and its superiority over traditional circuit switching for solving data communications needs, is analyzed. The paper concludes by describing a PBX implementation that takes advantage of circuit- and packet-switching technologies and thus offers a truly integrated multipurpose communications switch.