| 310 / | HD | ELECTRICAL GENERATOR OR MOTOR STRUCTURE |
| 300 | DF | NON-DYNAMOELECTRIC {4} |
| 311 | DF | .~ Piezoelectric elements and devices {17} |
| 341 | DF | .~.~ With temperature modifier and/or gas or vapor atmosphere control {3} |
| 342 | ![]() | .~.~.~ For plural piezoelectric elements |