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。
2.
The comparison of the computational results of flap movements indicates that three operational positions of the wing flaps guided through the different tracks are nearly close to each other and the non - arc - track is better to guide the flaps to the original three positions exactly 计算结果表明，不同的轨道下所得的襟翼3个工作位置从几何角度看比较接近，其中非圆弧轨道能够使襟翼在3个工作位置与预先设计的姿态完全相同。
