| 318 / | HD | ELECTRICITY: MOTIVE POWER SYSTEMS |
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| 560 | DF | POSITIONAL SERVO SYSTEMS (E.G., SERVOMECHANISMS) {23} |
| 638 | DF | .~ With particular "error-detecting" means {13} |
| 652 |  | .~.~ With particular position measuring instruments {7} |
| 653 | DF | .~.~.~> Magnetic transducers |
| 654 | DF | .~.~.~> Synchro control transmitter-transformer systems {1} |
| 656 | DF | .~.~.~> Differential transformer systems {5} |
| 662 | DF | .~.~.~> Variable capacitor systems |
| 663 | DF | .~.~.~> Potentiometer systems including autotransformers and Wheatstone bridges {4} |
| 669 | DF | .~.~.~> Standing wave |
| 670 | DF | .~.~.~> Contact resistance |