{HEAD ~ A transmitting unit} is coupled to {TAIL ~ the receiving unit} and transmits the data to an antenna 
{ HEAD ~ A transmitting unit } is coupled to { TAIL ~ the receiving unit } and transmits the data to an antenna
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH