with voice-band signalling frequencies

Full Title

Details of selecting apparatus or arrangements > Electrical details > Signalling arrangements; Manipulation of signalling currents (multiplex systems providing for calling or supervisory signals H04J1/14, H04J3/12) > using alternate current (H04Q1/50 takes precedence) > with voice-band signalling frequencies

Child Classifications

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• H04Q 1/446 using one signalling frequency (H04Q1/46 takes precedence)
• H04Q 1/45 using multi-frequency signalling (H04Q1/46 takes precedence)
• H04Q 1/46 comprising means for distinguishing between a signalling current of predetermined frequency and a complex current containing that frequency, e.g. speech current