US PATENT SUBCLASS 181 / 254
.~.~.~.~ Valve controlled

Current as of: June, 1999
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181 /   HD   ACOUSTICS

175  DF  SOUND-MODIFYING MEANS {12}
212  DF  .~ Muffler, fluid conducting type {25}
247  DF  .~.~ Straight-through passage {4}
253  DF  .~.~.~ With muffler bypass {1}
254.~.~.~.~ Valve controlled

DEFINITION

Classification: 181/254

Valve controlled:

(under subclass 253) Subject matter having means to vary the rate of fluid flow in either the through or the bypass passage.