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A hearing aid is a device used to help the hard-of-hearing hear sounds better. In the
past, a funnel-like amplification cone was used. Now, however, the most common style is
a small electronic device that fits into the wearer's ear. The first variety of this device had a rectangular battery pack connected by a thin wire, intended to be held in
a pocket. During the mid- to late 20th century, this type of power storage was replaced by a more inconspicuous sort in models in which small,
circular batteries were placed in the inserted unit itself.
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