| 379 / | HD | TELEPHONIC COMMUNICATIONS |
| 242 | DF | CENTRALIZED SWITCHING SYSTEM {15} |
| 258 | DF | .~ Switching controlled in response to called station addressing signal {9} |
| 268 | DF | .~.~ Having shared or common switching control {8} |
| 280 | DF | .~.~.~ Including registering or storing device for call address signal {7} |
| 285 | | .~.~.~.~ With magnetic memory |