door-bell and button system

例句：

1. 1. The doorbell rang,and the dog barked at the intruder.
   门铃响了，狗对着入侵者叫。
2. 2. The button system onthe remote controls is easy to use.
   遥控器上的按钮系统很容易使用。
3. 3. Thedoorbell was ringing, but no one answered.
   门铃在响，但没人回应。