381 / | HD | ELECTRICAL AUDIO SIGNAL PROCESSING SYSTEMS AND DEVICES |
150 | DF | ELECTRO-ACOUSTIC AUDIO TRANSDUCER {18} |
182 | DF | .~ Plural or compound reproducers {4} |
370 | .~.~ Headphone {3} | |
371 | DF | .~.~.~> Particular cup {2} |
374 | DF | .~.~.~> Particular support structure {9} |
384 | DF | .~.~.~> Electrical hardware feature |