| 340 / | HD | COMMUNICATIONS: ELECTRICAL |
| 500 | DF | CONDITION RESPONSIVE INDICATING SYSTEM {6} |
| 540 | DF | .~ Specific condition {18} |
| 541 | DF | .~.~ Intrusion detection {8} |
| 561 | DF | .~.~.~ Disturbance of electric field {1} |
| 562 | DF | .~.~.~.~ Capacitance {2} |
| 564 | | .~.~.~.~.~ Fence |