| 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} |
| 509 | DF | .~.~.~ Channel allocation {5} |
| 514 | ![]() | .~.~.~.~ Having storage detail |