voice frequency signalling current 音频振铃电流

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

single current signalling 单哩报 ; 单向电流信号

carrier-current signalling channel 载波通道

direct current signalling DC signalling 直流信令DC信令

direct current signalling code 直流信号标志

alternating current signalling AC signalling 交流信令AC信令

single-commutation direct-current signalling 单换向直流发信

double-current signalling [通信] 双流传信