speech plus voice frequency telegraph

例句：

1. 1. The speech plus voice frequency telegraph was used to transmit information over long distances.
   语音加频率电报被用来在长距离内传输信息。
2. 2. The invention of the speech plus voice frequency telegraph revolutionized communication.
   语音加频率电报的发明彻底改变了通信方式。
3. 3. The speech plus voice frequency telegraph proved to be a valuable tool for recording and transmitting audio signals.
   语音加频率电报证明了它是一个有价值的工具，用于录制和传输音频信号。