| 381 / | HD | ELECTRICAL AUDIO SIGNAL PROCESSING SYSTEMS AND DEVICES |
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| FOR 127 |  | HEARING AIDS, ELECTRICAL (381/68) {15} |
| FOR 128 | DF | .~> Directional (381/68.1) |
| FOR 129 | DF | .~> Frequency control (381/68.2) |
| FOR 130 | DF | .~> Bone conduction (381/68.3) |
| FOR 131 | DF | .~> Gain Control (381/68.3) |
| FOR 132 | DF | .~> Spectacle (381/68.5) |
| FOR 133 | DF | .~> Ear insert (381/68.6) |
| FOR 134 | DF | .~> Hook over ear (381/68.7) |
| FOR 135 | DF | .~> Specified casing or housing (381/69) {2} |
| FOR 138 | DF | .~> Having enclosure or housing (381/138) {1} |
| FOR 140 | DD | .~> With acoustic wave modifying structure (381/153) {5} |
| FOR 147 | DD | .~> Microphone (381/168) {2} |
| FOR 150 | DD | .~> Having body supported structure (e.g., earphone) (381/187) |
| FOR 151 | DD | .~> With mounting or support feature (381/188) |
| FOR 152 | DD | .~> Electromagnetic (e.g., dynamic) (381/192) {5} |
| FOR 165 | DD | .~> Electro-acoustical transducer mounting or support (381/205) |