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Invention Grant
US2217177A Loud-speaker 失效

  • Patent Title: Loud-speaker
  • Application No.: US17184237
    Application Date: 1937-10-30
  • Publication No.: US2217177A
    Publication Date: 1940-10-08
  • Inventor: FRANK MASSA
  • Applicant: RCA CORP
  • Assignee: RCA Corp
  • Current Assignee: RCA Corp
  • Priority: US17184237 1937-10-30
  • Main IPC: H04R9/02
  • IPC: H04R9/02
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