private branch exchange (PBX)

Small replica of a telephone exchange installed at a subscriber's premises, and connected via trunk lines to the telephone company's exchange. Depending on its capacity, a PBX can handle tens or hundreds of telephone lines, and reroute the incoming calls to the appropriate extension automatically or through an operator. Modern PBXs are built around a small computer, and some of them can be connected to a server for additional services such as call management, call-detail reports, telemarketing, etc. Also called private automatic branch exchange (PABX).