| 455 / | HD | TELECOMMUNICATIONS |
| 39 | DF | TRANSMITTER AND RECEIVER AT SEPARATE STATIONS {14} |
| 500 | DF | .~ Plural transmitters or receivers (i.e., more than two stations) {4} |
| 507 | DF | .~.~ Central station (e.g., master, etc.) {6} |
| 517 | DF | .~.~.~ To or from mobile station {5} |
| 523 | ![]() | .~.~.~.~ Using radiating transmission line |