H04Q1/446 - CPC Classification

Details of selecting apparatus or arrangements; Electrical details; Signalling arrangements; Manipulation of signalling currents using alternate current with voice-band signalling frequencies using one signalling frequency

• H04Q1/4465 » {the same frequency being used for all signalling information, e.g. A.C. nr.9 system} 0
• H04Q1/448 » with conversion of a single frequency signal into a digital signal 0