信号器

例句：

1. 1. The policeman used a signal light to warn the driver of an impending accident.
   警察使用一个信号灯来警告即将发生事故的司机。
2. 2. The traffic officer flashed his hand as a signal for the drivers to slow down.
   交通官员挥手作为减速的信号。
3. 3. The firefighters used smoke signals to alert the nearby residents of the fire danger.
   消防员使用烟雾信号来警告附近的居民火灾危险。