379 / | HD | TELEPHONIC COMMUNICATIONS |
1 | DF | DIAGNOSTIC TESTING, MALFUNCTION INDICATION, OR ELECTRICAL CONDITION MEASUREMENT {12} |
9 | DF | .~ Of centralized switching system {6} |
15 | DF | .~.~ Of automatic switching equipment {4} |
19 | ![]() | .~.~.~ Rapid manual connecting structure for test equipment |