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