{HEAD ~ Control electronics} in each rack communicate with and provide power to the control electronics of {TAIL ~ 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 ~ Control electronics } in each rack communicate with and provide power to the control electronics of { TAIL ~ 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 OTH OTH OTH OTH OTH OTH 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