A second coding device is located in the write path and removes runs of {HEAD ~ zeros} in {TAIL ~ interleaved subsequences} in the scrambled user data 
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A second coding device is located in the write path and removes runs of { HEAD ~ zeros } in { TAIL ~ interleaved subsequences } in the scrambled user data
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH