| 340 / | HD | COMMUNICATIONS: ELECTRICAL |
| 500 | DF | CONDITION RESPONSIVE INDICATING SYSTEM {6} |
| 540 | DF | .~ Specific condition {18} |
| 686.1 | | .~.~ Position responsive {9} |
| 687 | DF | .~.~.~> Connected or disconnected |
| 688 | DF | .~.~.~> Meter dial |
| 689 | DF | .~.~.~> Tilt |
| 690 | DF | .~.~.~> Geophysical (e.g., fault slip) |
| 686.2 | DF | .~.~.~> Alignment or misalignment |
| 686.3 | DF | .~.~.~> Shaft or rotary element |
| 686.4 | DF | .~.~.~> One article inserted into another |
| 686.5 | DF | .~.~.~> Workpiece |
| 686.6 | DF | .~.~.~> Proximity or distance |