{HEAD ~ a receptor} at {TAIL ~ the opposite side} of said third rail from said laser diode 
at
{ HEAD ~ a receptor } at { TAIL ~ the opposite side } of said third rail from said laser diode
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH