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Abstract

A subcarrier to horizontal sync (SC/H) phase difference measurement and display device for multiple sources of composite video signals includes a sample clock generator providing a sampling clock at a fixed frequency, a digitizer providing numeric samples representing an amplitude of each of the sources at least during the interval between the horizontal sync pulse and the color burst of at least one horizontal line in each of the sources. The samples are stored in memory and a processor compares successive samples, while counting samples or monitoring elapsed time, to find the midpoint of the leading edge of the sync pulse and a zero crossing of the burst. The lapse of time (or number of samples) defines the SC/H phase difference and is displayed for all of the sources for direct graphic comparison. The digitizer, memory, processor and display are coupled over a data bus. A line counter responsive to horizontal syncs in each source, reset upon vertical retrace, triggers capture of the data at a selected horizontal line, which can be different for the respective sources, and the line numbers are displayed together with the graphic comparison.

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First Claim