CENTRal EXchange. Telephone company service that renders obsolete the need of buying, maintaining, and upgrading a private branch exchange (PBX). Essentially, Centrex service consists of ordinary trunk lines with several features added by the phone company. These features include the common four: call conferencing, call forwarding , call waiting, and speed calling, as well as others such as call accounting , caller ID, call hold, call transfer, direct inward dialing, intercom, least cost routing, and so on. More economical than a PBX system, Centrex does require special telephone equipment for exploiting its features.
Black’s Law Online Dictionary
