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