A window unit frame is received in {HEAD ~ each clear window opening} supported by and electrically connected to {TAIL ~ the frame} 
A window unit frame is received in { HEAD ~ each clear window opening } supported by and electrically connected to { TAIL ~ the frame }
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL