signal bridge

例句：

1. 1. The policeman used his flashlight to signal the driver to stop.
   警察用他的手电筒示意司机停车。
2. 2.The traffic light is a common signal for pedestrians crossing the street.
   交通灯是行人过马路的常见信号。
3. 3. The pilot used a flare to signal the plane's altitude and direction.
   飞行员使用信号弹来指示飞机的高度和方向。