| 327 / | HD | MISCELLANEOUS ACTIVE ELECTRICAL NONLINEAR DEVICES, CIRCUITS, AND SYSTEMS |
| 1 | DF | SPECIFIC SIGNAL DISCRIMINATING (E.G., COMPARING, SELECTING, ETC.) WITHOUT SUBSEQUENT CONTROL {11} |
| 28 | DF | .~ By polarity {2} |
| 29 | | .~.~ Selection of a particular polarity |