first indicator means connected to said back up safety means operable to indicate connection of said back up safety means to {HEAD ~ a source} of {TAIL ~ energy} 
of
first indicator means connected to said back up safety means operable to indicate connection of said back up safety means to { HEAD ~ a source } of { TAIL ~ energy }
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 REL TAIL TAIL TAIL TAIL TAIL