Public automatic branching exchange ( pabx ) a telephone system installed in atcx for efficient communications between operational positions in the atcx and external parties through the public service telephone network . microwave link system ( mls ) 这套在航空交通管制大楼内安装的电话系统，可为管制岗位提供更有效率的内部通讯，同时，透过公共电话网络服务，也可对外作快捷的通话。
