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