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