US PATENT SUBCLASS 181 / *
SPEAKING TUBES

Current as of: June, 1999
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181 /   HD   ACOUSTICS

*SPEAKING TUBES {5}
18  DF  .~> Systems
19  DF  .~> Alarms and indicators
20  DF  .~> Combined mouth and ear pieces
21  DF  .~> Mouthpieces
22  DF  .~> Tubes