During each scan line of {TAIL ~ regular scanning}, dark cells are sampled and produce a voltage that is modified by the offset voltage that was determined during {HEAD ~ calibration} 
During each scan line of { TAIL ~ regular scanning } , dark cells are sampled and produce a voltage that is modified by the offset voltage that was determined during { HEAD ~ calibration }
OTH OTH OTH OTH OTH 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 OTH HEAD HEAD HEAD HEAD HEAD