| 摘要 |
1510870 Carbon microphones SIEMENS AG 15 July 1975 [19 Aug 1974(2)] 29598/75 Heading H4J In a carbon microphone of the type disclosed in Specification 957,384 wherein part of the chamber containing the carbon granules is closed by an air permeable pit 10, and a folded sleeve 11 is provided which is impermeable to moisture, the edge of the foil 10 is arranged to be surrounded by moisture impermeable material 11, 12. The material 12 may be formed integrally with the sleeve 11 or may be formed as a separate ring of material.
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