a thyristor free wheeling diode connected in {TAIL ~ antiparallel relationship} with {HEAD ~ the respective thyristor} 
a thyristor free wheeling diode connected in { TAIL ~ antiparallel relationship } with { HEAD ~ the respective thyristor }
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD