When system power is depleted to a defined level, the primary processor is shut down and certain operations are taken over by {HEAD ~ a low power, secondary processor} that operates using {TAIL ~ a secondary operating system} 
When system power is depleted to a defined level , the primary processor is shut down and certain operations are taken over by { HEAD ~ a low power , secondary processor } that operates using { TAIL ~ a secondary operating system }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL