US PATENT SUBCLASS 381 / 319
.~ With vacuum tube amplifier

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

312  DF  HEARING AIDS, ELECTRICAL {9}
319.~ With vacuum tube amplifier

DEFINITION

Classification: 381/319

With vacuum tube amplifier:

(under subclass 312) Subject matter including means using one or more devices in which electron flow takes place in an evacuated envelope.

SEE OR SEARCH CLASS

330, Amplifiers,

64, for vacuum tube amplifiers generally.