During {HEAD ~ 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 calibration 
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During { HEAD ~ 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 calibration
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL 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 OTH