{HEAD ~ Control electronics} in each rack communicate with and provide power to {TAIL ~ the control electronics} of each corresponding box, and control electronics in each freezer communicate with and provide power to the control electronics of each corresponding rack, and a host computer communicates with the control electronics in each freezer 
communicate with
{ HEAD ~ Control electronics } in each rack communicate with and provide power to { TAIL ~ the control electronics } of each corresponding box , and control electronics in each freezer communicate with and provide power to the control electronics of each corresponding rack , and a host computer communicates with the control electronics in each freezer
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL REL OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH