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