同义词
1)Private Branch Exchange(PBX),企业用户专用交换机2)private exchange,private branch exchange,专用交换机，用户交换机3)private exchange,专用交换机;用户交换机4)private branch switchboard,用户总机，用户交换台，专用交换台5)centrex Centralized Extension System,集中式用户专用交换机6)Private Branch Exchange PBX,用户交换机,专用交换机,小交换机
