{TAIL ~ The digital data} comprises a preamble field followed by {HEAD ~ a sync mark} followed by a data field 
{ TAIL ~ The digital data } comprises a preamble field followed by { HEAD ~ a sync mark } followed by a data field
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH