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