When {TAIL ~ the known code portion} is not detected from {HEAD ~ the coded data}, the coded data will be decoded 
When { TAIL ~ the known code portion } is not detected from { HEAD ~ the coded data } , the coded data will be decoded
OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH