Threshold detection
AssigneeBell Telephone Laboratories, Incorporated
InventorStephen J. Brolin
Life of this patent
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Abstract
A simple and inexpensive direct current voltage level detector is shown which has a significant immunity against interfering alternating current signal components. The output of a standard analog threshold detector is successively sampled by clock pulses having twice the repetition rate of the frequency of the expected interfering alternating current components. By requiring two successive samples to be above the threshold of detection, immunity is provided against false detection due to temporarily exceeding the threshold level due solely to the positive excursion of the interfering alternating current components. Simple clock-driven flip-flops are used for the sampling and a simple logical AND gate is used to detect the successive samples.
Claims4
A direct current threshold level detector for detecting a direct current threshold level in the presence of interfering alternating current components and including a direct current threshold level detector (10)
- characterized by
- a source of clock pulses (17) at a repetition rate equal to twice the frequency of said interfering alternating current components,
- means for sampling the output of said level detector with said clock pulses (11,14), and
- means for detecting the presence to two successive outputs from said sampling means (15).
Dependencies are inferred from the claim text.