manual signal box

例句：

1. 1. The manual signal box is used to indicate the presence of an emergency vehicle.
   手动信号箱用于指示紧急车辆的存在。
2. 2. The manual signal box was designed to prevent accidents caused by distracted driving.
   手动信号箱被设计来防止由分心驾驶引起的事故。
3. 3. The manual signal box is commonly found in construction sites, where it helps workers communicate with each other.
   手动信号箱在建筑工地中很常见，帮助工人相互沟通。