| 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 | DF | .~.~.~ Plural input channels of different rates to a single common rate output channel {1} |
| 539 | | .~.~.~.~ Multiple levels of multiplexing to form a multiplex hierarchy |