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