| 340 / | HD | COMMUNICATIONS: ELECTRICAL |
| 500 | DF | CONDITION RESPONSIVE INDICATING SYSTEM {6} |
| 540 | DF | .~ Specific condition {18} |
| 584 | DF | .~.~ Thermal {8} |
| 595 | ![]() | .~.~.~ Current modifier or generator {4} |
| 596 | DF | .~.~.~.~> Cable or elongated probe |
| 597 | DF | .~.~.~.~> Curie point sensor |
| 598 | DF | .~.~.~.~> Barrier-layer sensor |
| 599 | DF | .~.~.~.~> Bridge circuit |