call signal apparatus

例句：

1. 1.The new call signal apparatus has greatly improved our communication efficiency.
   新的呼叫信号装置大大提高了我们的通信效率。
2. 2. The engineers were busy installing the new call signal apparatus.
   工程师们忙于安装新的呼叫信号装置。
3. 3. The call signal apparatus was used to alert the authorities of an emergency situation.
   呼叫信号装置被用来向当局发出紧急情况的警报。