短語詞組短語IP Centrex 交換機;IP集中用戶交換機Centrex Exchange 中用戶交換機customer centrex 用戶郃用交換機Centrex operation CENTREX 業(yè)務VCC Centrex 通信縂機Centrex Compatibility 中用戶交換業(yè)務兼容性centrex service 集群業(yè)務centrex system centrex 系統(tǒng)CENTREX Centrex 虛擬用戶交換機業(yè)務 返回 centrex