When the threshold level VREF·1 is set slightly lower than {HEAD ~ the level V1} of {TAIL ~ white}, a video signal 36 is obtained in which red, blue and black are in the L level state 
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When the threshold level VREF·1 is set slightly lower than { HEAD ~ the level V1 } of { TAIL ~ white } , a video signal 36 is obtained in which red , blue and black are in the L level state
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH