379 / | HD | TELEPHONIC COMMUNICATIONS |
242 | DF | CENTRALIZED SWITCHING SYSTEM {15} |
258 | DF | .~ Switching controlled in response to called station addressing signal {9} |
298 | DF | .~.~ Direct control {3} |
299 | DF | .~.~.~ Step-by-step system {4} |
302 | .~.~.~.~ Having rotary switch |