| 342 / | HD | COMMUNICATIONS: DIRECTIVE RADIO WAVE SYSTEMS AND DEVICES (E.G., RADAR, RADIO NAVIGATION) |
| 350 | DF | DIRECTIVE {10} |
| 450 | DF | .~ Position indicating (e.g., triangulation) {11} |
| 463 | DF | .~.~ Having plural transmitters or receivers {2} |
| 464 | | .~.~.~ Plural transmitters only |