| 455 / | HD | TELECOMMUNICATIONS | 
| 403 | DF | RADIOTELEPHONE SYSTEM {12} | 
| 422 | DF | .~ Zoned or cellular telephone system {14} | 
| 450 |  | .~.~ Channel allocation {4} | 
| 451 | DF | .~.~.~> Hybrid allocation | 
| 452 | DF | .~.~.~> Dynamic allocation | 
| 453 | DF | .~.~.~> Load balancing | 
| 454 | DF | .~.~.~> Spectrum sharing for different type of system (e.g., point-to-point microwave, television, etc.) |