| 370 / | HD | MULTIPLEX COMMUNICATIONS | 
| 464 | DF | COMMUNICATION TECHNIQUES FOR INFORMATION CARRIED IN PLURAL CHANNELS {9} | 
| 498 | DF | .~ Combining or distributing information via time channels {17} | 
| 537 | DF | .~.~ Multiplexing plural input channels to a common output channel {2} | 
| 538 |  | .~.~.~ Plural input channels of different rates to a single common rate output channel {1} | 
| 539 | DF | .~.~.~.~> Multiple levels of multiplexing to form a multiplex hierarchy |