crystal frequency indicator

例句：

1. 1.This crystal frequency indicator is used to measure the frequency of light waves in a particular medium.
   这个晶体频率指示器是用来测量特定介质中光波的频率的。
2. 2.The crystal frequency indicator was used to detect the presence of foreign objects in the air.
   晶体频率指示器被用来检测空气中外来物体的存在。
3. 3.The crystal frequency indicator was used to monitor the stability of the electronic circuits.
   晶体频率指示器被用来监测电子电路的稳定性。