| 219 / | HD | ELECTRIC HEATING | 
| 50 | DF | METAL HEATING (E.G., RESISTANCE HEATING) {19} | 
| 121.11 | DF | .~ By arc {16} | 
| 130.1 | DF | .~.~ Including arc-power supplies {5} | 
| 130.21 | DF | .~.~.~ With automatic output control (e.g., shortcircuit, infrared) {3} | 
| 130.32 |  | .~.~.~.~ Responsive to arc current only |