下课铃

xià kè líng dǎ le lǎo shī hái zài tāo tāo bù jué de tuō táng

下课铃打了，老师还在滔滔不绝地拖堂。

The teacher was still holding forth after the bell had rung.

xià kè líng xiǎng le

下课铃响了。

The bell sounded for the end of the class.