| 123 / | HD | INTERNAL-COMBUSTION ENGINES |
| 311 | DF | FOUR-CYCLE {19} |
| 80 R | ![]() | .~ Rotating valve {5} |
| 80 BA | DF | .~.~> Rotary valve is perpendicular to cylinder |
| 80 BB | DF | .~.~> Rotary valve is parallel to cylinder |
| 80 C | DF | .~.~> Sleeve valve |
| 80 D | DF | .~.~> Disc valve |
| 80 DA | DF | .~.~> Rotary plug |