signal maintenance depot

例句：

1. 1.The policeman used his flashlight to signal the driver to stop.
   警察用他的手电筒向司机示意停车。
2. 2. The traffic light is a common signal for drivers to follow.
   交通灯是司机们常用的指示信号。
3. 3.The pilot used a signal to guide the plane safely into the runway.
   飞行员使用信号引导飞机安全地进入跑道。