| 307 / | HD | ELECTRICAL TRANSMISSION OR INTERCONNECTION SYSTEMS |
| 149 | | MISCELLANEOUS SYSTEMS {5} |
| 150 | DF | .~> Power packs |
| 151 | DF | .~> Conversion systems |
| 152 | DF | .~> Rate of change responsive systems |
| 153 | DF | .~> Generator control systems |
| 154 | DF | .~> For particular load device {2} |