363 / | HD | ELECTRIC POWER CONVERSION SYSTEMS |
157 | DF | FREQUENCY CONVERSION (f1-f2) WITHOUT INTERMEDIATE CONVERSION TO D.C. {7} |
166 | DF | .~ By electron tube converter {1} |
167 | DF | .~.~ With discharge control means {2} |
168 | .~.~.~ Including plural anodes and single cathode device (e.g., vapor arc device) |