| 327 / | HD | MISCELLANEOUS ACTIVE ELECTRICAL NONLINEAR DEVICES, CIRCUITS, AND SYSTEMS |
| 1 | DF | SPECIFIC SIGNAL DISCRIMINATING (E.G., COMPARING, SELECTING, ETC.) WITHOUT SUBSEQUENT CONTROL {11} |
| 50 | DF | .~ By amplitude {9} |
| 51 | DF | .~.~ With sensing amplifier {2} |
| 52 | DF | .~.~.~ Differential amplifier {3} |
| 54 | | .~.~.~.~ Having feedback {1} |
| 55 | DF | .~.~.~.~.~> Cross-coupled |