Importance

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Abstract

A circuit for ascertaining the direction of origin of the most significant transient appearing on a electrical power line within a predetermined interval is disclosed. Threshhold comparator circuit (325, 326) are provided to insure that transient polarities needed for the directivity determination are ascertained while the transient impulse is still rising towards its peak value. For any nominal, user-set threshhold (V.sub.2), a lower preliminary threshold (V.sub.1) is automatically set and when the transient exceeds the preliminary threshhold, the transient polarities are determined and correlated to effect a tentative directivity determination which is stored in an input latch (205). When the transient exceeds the nominal threshhold, the directivity determination is transferred to an output latch (211) to be read by an output printing device. If a larger transient occurs before the directivity of a previous transient has been read by the output printing device, directivity data for the larger transient is substituted in the latches (205, 211). A dynamic feedback mechanisms (C+, 122, R61, VPO, R30, R23) increases the effective threshholds for the comparator circuits (326, 325) in accordance with the peak value of the largest transient occurring during the predetermined interval.

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First Claim