CIRCUIT FOR DETECTING PRESENCE OR ABSENCE OF REPETITIVE PULSE WITH CONSTANT PERIOD

PURPOSE:To detect easily and surely an erroneous pulse by providing the 1st and 2nd comparator circuits comparing respectively an integration output from an integration circuit with the 1st and 2nd reference values when a high level period or a low level period of a peak value of a pulse exceeds a prescribed period. CONSTITUTION:The comparator circuits 16, 18 are provided, which compare respectively an integration output (b) from the integration circuit 8 with a reference value (d) or (c) when a high level period or a low level period of a peak value of a pulse (a) exceeds respectively a prescribed period T2 or T1. Thus, even when the peak value of the pulse (a) is either a low level or a high level, when the period is within a prescribed period T1 (T2), the comparator circuits 16, 18 both output a high level as shown in t1, t2 in figure. When the high level of the peak exceeds the prescribed period T2, the output level of the comparator circuit 16 goes to a low level as shown in t3 in figure, and when the low level of the peak exceeds the prescribed period T1, the output level of the comparator circuit 18 goes to a low level as shown in t4 in figure. Thus, an erroneous pulse is detected in this way.