The earth key detector and its manner in order to detect the earth key operation of the telephone with resistance coherence.

摘要

(57) The [Abstract] The present invention relates to a ground key detection circuit for detecting a ground key operation of the telephone in a manner that is resistant to interference, the present invention is flowing when the grounding key (6) is operated period, that period the longitudinal current exceeds the current threshold, and the comparison instruments for comparing the threshold longitudinal current detection device for detecting a longitudinal current (4), a vertical current detected (6), exceeds less than period, that it includes monitoring circuit for detecting the period of longitudinal current drops below the current threshold value (8). I want to output a ground key detection signal when longer than the period of time period is below exceeded (8) monitor circuit.