voice-frequency signalling 音频信号方式

single-frequency signalling [通信] 单频发信

suppressed frequency signalling system 频率压缩信号系统

two-frequency signalling 双频制信号

voice frequency signalling current 音频振铃电流

voice-frequency signalling current [电子] 音频信号电流

voice frequency signalling system 音频信号传输系统

one-frequency signalling 单频信号方式

signalling tone peak frequency deviation 信令音峰值频偏