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Class Information
Number: 181/138
Name: Acoustics > Mechanical telephone
Description: Subject matter wherein sound is transmitted by the vibrations of molecules set up by mechanical means in a wire, string or flexible member strung taut.

Patents under this class:

Patent Number Title Of Patent Date Issued
5579398 Electro-acoustic transducer Nov. 26, 1996
5127870 Echo-type toy megaphone Jul. 7, 1992
4195707 Communicating device Apr. 1, 1980
4194095 Fluid flow control speaker system Mar. 18, 1980
4187635 Method and apparatus for sound production Feb. 12, 1980
4002897 Opto-acoustic telephone receiver Jan. 11, 1977

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