US PATENT SUBCLASS 381 / 180
.~.~.~ Granular or carbon

Current as of: June, 1999
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381 /   HD   ELECTRICAL AUDIO SIGNAL PROCESSING SYSTEMS AND DEVICES

150  DF  ELECTRO-ACOUSTIC AUDIO TRANSDUCER {18}
369  DF  .~ Microphone capsule only {10}
179  DF  .~.~ Resistive {1}
180.~.~.~ Granular or carbon {1}
181  DF  .~.~.~.~> Differential

DEFINITION

Classification: 381/180

Granular or carbon:

(under subclass 180) Subject matter having a sound responsive resistive element composed of either elemental carbon, or a mass of comminuted material.