to prep.对于；为了；(表示方向)到；向；(表示间接关系)给adv.（表示方向）去；（门）关上
双语例句
An electronic device that converts one frequency of a radio signal to another. 变频器将无线电讯号从一种频率转换成另一种频率的电子装置
I'll cue you in (ie give you a signal to start) by nodding my head. 我一点头，你就开始。
It is the simplest signal to make, in time of danger or disaster. 这是在遇到危险或灾难的时候能发出的最简单的信号。
An extract from the music for another part printed, usually in smaller notes, within a performer's part as a signal to enter after a long rest. 提示小节在乐谱中为另一声部作准备的选段，通常用较小的字体印刷，在演奏部分之内，作为在长时间休息后另一声部进入的信号
