{HEAD ~ The incandescent filament lamps} are electrically connected in series and powered by {TAIL ~ an AC power supply} 
are powered by
{ HEAD ~ The incandescent filament lamps } are electrically connected in series and powered by { TAIL ~ an AC power supply }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL