In addition, a third subsystem and {HEAD ~ fourth subsystem} have S copies of {TAIL ~ the data line} 
In addition , a third subsystem and { HEAD ~ fourth subsystem } have S copies of { TAIL ~ the data line }
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL