| 摘要 |
A hearing aid includes an electronic amplifier, an electric power source and a switch for automatically breaking or making the connection between the amplifier and the power source depending on whether the hearing aid is in use or out of use. The switch is provided in such a manner so as to be responsive to switching criterion defined by a change of state such as change in temperature, moisture etc. The switch is disposed at a wall surface which is subjected to the change of state.
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