| 307 / | HD | ELECTRICAL TRANSMISSION OR INTERCONNECTION SYSTEMS |
| 43 | DF | PLURAL SUPPLY CIRCUITS OR SOURCES {14} |
| 44 | DF | .~ One source floats across or compensates for other source {3} |
| 45 | DF | .~.~ With intervening converter {1} |
| 46 | ![]() | .~.~.~ Storage battery or accumulator-type source |