crystal tube

例句：

1. 1.The crystal tube is used to transmit sound waves.
   水晶管用于传输声波。
2. 2. The crystal tube was the first device to transmit sound through the air.
   水晶管是第一个通过空气传输声音的设备。
3. 3. The crystal tube was used in the early days of radio transmission.
   水晶管在早期无线电传输中使用。