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