{HEAD ~ Voltage converter} with {TAIL ~ GTO thyristors} in series connection with at least a choke with freewheeling circuit 
with
{ HEAD ~ Voltage converter } with { TAIL ~ GTO thyristors } in series connection with at least a choke with freewheeling circuit
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH