at least one snubber capacitor connected in {HEAD ~ series} with {TAIL ~ the thyristor circuit diode} in parallel with the respective gate turn off thyristor, and 
at least one snubber capacitor connected in { HEAD ~ series } with { TAIL ~ the thyristor circuit diode } in parallel with the respective gate turn off thyristor , and
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH