{HEAD ~ A symbol} interleaver communicates with the first divider and interleaves the first and second symbols when the first interleaved subsequences of {TAIL ~ the first and second symbols} are all zeros or the second interleaved subsequences of the first and second symbols are all zeros 
{ HEAD ~ A symbol } interleaver communicates with the first divider and interleaves the first and second symbols when the first interleaved subsequences of { TAIL ~ the first and second symbols } are all zeros or the second interleaved subsequences of the first and second symbols are all zeros
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 TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH