| 310 / | HD | ELECTRICAL GENERATOR OR MOTOR STRUCTURE |
| 300 | DF | NON-DYNAMOELECTRIC {4} |
| 311 | DF | .~ Piezoelectric elements and devices {17} |
| 328 | DF | .~.~ With mechanical energy coupling means {6} |
| 334 | DF | .~.~.~ Acoustic wave type generator or receiver {3} |
| 336 | ![]() | .~.~.~.~ Nondestructive testing type |