| 310 / | HD | ELECTRICAL GENERATOR OR MOTOR STRUCTURE |
| 300 | DF | NON-DYNAMOELECTRIC {4} |
| 311 | DF | .~ Piezoelectric elements and devices {17} |
| 313 R | DF | .~.~ Surface acoustic wave devices {2} |
| 313 B | DF | .~.~.~ Interdigitated electrodes {2} |
| 313 C | ![]() | .~.~.~.~ Envelope or apodized |