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