307 / | HD | ELECTRICAL TRANSMISSION OR INTERCONNECTION SYSTEMS |
112 | DF | SWITCHING SYSTEMS {5} |
116 | DF | .~ Condition responsive {4} |
119 | DF | .~.~ Mechanical force {1} |
120 | DF | .~.~.~ Speed, centrifugal or kinetic force {4} |
123 | .~.~.~.~ Differential speed between two bodies |