| 381 / | HD | ELECTRICAL AUDIO SIGNAL PROCESSING SYSTEMS AND DEVICES |
| 150 | DF | ELECTRO-ACOUSTIC AUDIO TRANSDUCER {18} |
| 396 | DF | .~ Electromagnetic (e.g., dyynamic) {8} |
| 400 | DF | .~.~ Movable voice coil {8} |
| 401 | ![]() | .~.~.~ Multiple voice coils {1} |
| 402 | DF | .~.~.~.~> For different frequencies |