| 313 / | HD | ELECTRIC LAMP AND DISCHARGE DEVICES |
| 118 | DF | SPARK PLUGS {22} |
| 130 | DF | .~ Non-conducting material in or adjacent gap (e.g., restricts spark) {1} |
| 131 R | DF | .~.~ Non-shortest line spark and surface spark type {1} |
| 131 A | ![]() | .~.~.~ Spark plugs with semiconductive material at the gap |