Method and {HEAD ~ apparatus} for producing {TAIL ~ grey levels} on a raster scan video display device 
for producing
Method and { HEAD ~ apparatus } for producing { TAIL ~ grey levels } on a raster scan video display device
OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH