{HEAD ~ The digital signals} are introduced to {TAIL ~ a digital carrier recovery loop} and a digital symbol recovery loop 
are introduced to
{ HEAD ~ The digital signals } are introduced to { TAIL ~ a digital carrier recovery loop } and a digital symbol recovery loop
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH