英语达人,我又来了啊,An electron tube is a device that can block,ampli

英语达人,我又来了啊,
An electron tube is a device that can block,amplify,or act as an on/off switch for an electric current.好像没有switch for 的词组吧,也就是说 这几个功能都是for an electric current 的.比如 block for an electric current ,amplify for an electric current ,act as an on/off switch for an electric current.是不是?我语法很烂!