振铃信号频率

ING l video frequency signal generator signal frequency shift signal frequency multiplier frequency modulated signal demodulator of frequency shift signal L segregate L/C L-plate L/Cpl l-driver emergency signal(l)ing signal(l)ing speed signal(l)ing rate signal(l)ing signal(l)ing test signal(l)ing condition signal(l)ing channel forward signal(l)ing path audible signal(l)ing device signal(l)ing-equipment test signal(l)ing-nework-management signal