voice frequency telegraphy equipment 音频电报设备

Voice-frequency telegraphy on radio circuits 无线电路上的音频电报

multi-channel voice-frequency telegraphy 多路音频电报

single channel voice frequency telegraphy 单路音频电报

voice-frequency carrier telegraphy 音频载波电报术

voice frequency multi-channel carrier telegraphy 音频多信道载波电报

voice-frequency multiplex telegraphy 音频复用电报

multi-channel telegraphy voice frequency 声频多路电报术

voice e frequency telegraphy 音频电报