signal approach control circuit

例句：

1. 1. The traffic policeman used his flashlight to signal the driver to stop.
   交通警察用他的手电筒示意司机停车。
2. 2. The new sign was erected at the entrance of the museum.
   博物馆入口处竖立了新的标牌。
3. 3.The beacon on the ship guided the lost sailors back to safety.
   船上的灯塔指引迷失的水手安全返回。