clapper switch

例句：

1. 1. The clock has a clapper switch on it for easy adjustment.
   这台钟有一个扣子开关，便于调整时间。
2. 2. The old house had a clapper switch in the kitchen.
   那所旧房子厨房里有一个扣子开关。
3. 3.The car's engine was running smoothly with the clapper switch turned off.
   汽车发动机在关闭了扣子开关后运行得非常平稳。