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