Dual polarity pulse detection circuit with variable voltage threshold

Claim 1

A circuit for detecting input signals of of positive and negative polarities and displaying a stretched pulse visibly indicating the occurrence of said input signals relative to a reference signal, said circuit comprising: threshold signal means for providing a threshold signal; comparator means having an input, a reference and an output terminal, said input terminal being coupled to receive said input signals and said reference terminal being coupled to receive said threshold signal, the comparator means being effective for detecting the level of each of the input signals relative to the level of said reference signal and for producing at said output terminal an output pulse indicative of the input signal level relative to the reference signal level; pulse stretching means capacitively coupling said output terminal to said reference terminal for providing capacitive feedback of the output pulse, said capacitively fed-back output pulse combining with said threshold signal to form the reference signal, said reference signal being applied to the reference terminal causing the comparator means to produce a stretched output pulse of increased duration in response to the output pulse having a duration shorter than a predetermined value; and display means coupled to the output terminal of said comparator means for producing discretely visible indications of said stretched output pulse.