In general the number of switching modules need not be same as {HEAD ~ the number} of {TAIL ~ switching controllers} 
of
In general the number of switching modules need not be same as { HEAD ~ the number } of { TAIL ~ switching controllers }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL