frequency odulation telecommunication system

例句：

1. 1. The frequencyof occurrence is 50%.
   发生的频率是50%。
2. 2. The frequency of lightwaves is measured in hertz.
   光波的频率是以赫兹为单位测量的。
3. 3. Thefrequency of the signal changes with time.
   信号的频率随时间变化。