Direction finding ( df ) equipment a vhf radio station which generates a bearing line on the radar display when an aircraft transmits . it facilitates air traffic controllers to identify aircraft operating within his area of jurisdiction 它可在飞机发出通讯讯号时，在雷达屏幕上显示出该飞机的方向线，以协助航空交通管制员确认其所管制范围内之飞机。
