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