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