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