Individual sensors sense the magnitude of {HEAD ~ a variable power component} from {TAIL ~ each power source} and provide a signal proportional thereto 
from
Individual sensors sense the magnitude of { HEAD ~ a variable power component } from { TAIL ~ each power source } and provide a signal proportional thereto
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH