US PATENT SUBCLASS 381 / FOR 136
.~.~ Having vacuum tube amplifier (381/69.1)

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

FOR 127  DF  HEARING AIDS, ELECTRICAL (381/68) {15}
FOR 135  DF  .~ Specified casing or housing (381/69) {2}
FOR 136.~.~ Having vacuum tube amplifier (381/69.1)

DEFINITION

Classification: 381/FOR.136

Having vacuum tube amplifier:

Subject matter including an amplifier which uses one or more electron tubes.