One virtual backplane system includes {HEAD ~ a bus}, and first and second line cards coupled to {TAIL ~ the bus} 
One virtual backplane system includes { HEAD ~ a bus } , and first and second line cards coupled to { TAIL ~ the bus }
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL