多路音频电报制
multi-channel vioce frequency telegraphy
音频多路电报术
voice-frequency-multichannel telegraphy
中音频
sound intermediate frequency
SIF
窄带音频信号
narrowband audio frequency signal
窄带音频加密机
narrow-band audio encryption unit
音频自动分类
automatic audio classification
音频转发器
VFREP Voice Frequency REPeater
音频专线
Leased line of voice frequency