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