动名词短语在下面句子中的作用?
问题描述：
动名词短语在下面句子中的作用?
we measure the zero-crossing times of the Manchester encoded signal using a comparator at Vcc/2 (后面的这个动名词短语在这里起到了什么作用呢?)driving the input line of a timer capture unit sensitive on both rising and falling edges.
答
at Vcc/2 that/which drives the input line of a.省略定语从句主语故用driving做定语