警报器

例句：

1. 1.The alarm clock woke us up at 6:00 a.m.
   闹钟在早上6点叫醒了我们。
2. 2.The police were called to the scene of the accident.
   警察被叫到事故现场。
3. 3. I set off an alarm when I locked the door.
   我锁门的时候触发了报警器。