The usefulness of {TAIL ~ the system} 100 may be greatly extended by switching to the secondary processor when battery power reaches {HEAD ~ a predetermined level} 
The usefulness of { TAIL ~ the system } 100 may be greatly extended by switching to the secondary processor when battery power reaches { HEAD ~ a predetermined level }
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD