{HEAD ~ A video signal} and a horizontal synchronizing signal provided from a work station are delayed by {TAIL ~ a plurality} of delay circuits having different delay amounts, and phase differences between a sampling clock signal and the delayed signals are detected 
are delayed by
{ HEAD ~ A video signal } and a horizontal synchronizing signal provided from a work station are delayed by { TAIL ~ a plurality } of delay circuits having different delay amounts , and phase differences between a sampling clock signal and the delayed signals are detected
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