Each of the EDUs, keypad controllers and CCIs of {TAIL ~ the system} is connected to {HEAD ~ a common communication bus} 
Each of the EDUs , keypad controllers and CCIs of { TAIL ~ the system } is connected to { HEAD ~ a common communication bus }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD