| 381 / | HD | ELECTRICAL AUDIO SIGNAL PROCESSING SYSTEMS AND DEVICES |
| 150 | DF | ELECTRO-ACOUSTIC AUDIO TRANSDUCER {18} |
| 182 | DF | .~ Plural or compound reproducers {4} |
| 370 | DF | .~.~ Headphone {3} |
| 374 | DF | .~.~.~ Particular support structure {9} |
| 378 | | .~.~.~.~ Single band |