Audiotone Model A-28 "Pinal" Behind-the-Ear Transistor Hearing Aid The Audiotone Model A-28 "Pinal" behind-the-ear (BTE) transistor hearing aid was made by Audiotone, Inc. of Phoenix, AZ in 1975. The Audiotone Model A-28 measured 1¾" x 9/16" x ½" (4.4 x 1.9 x 1.2 cm) and weighed 0.1 oz. (4 g) without the battery. |  | Click picture for larger view | | | | | |
| Side view of the Audiotone Model A-28 "Pinal" behind-the-ear (BTE) transistor hearing aid showing main body (left), ear hook (top right) and ear mold (right).
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| Rear view of the Audiotone Model A-28 "Pinal" behind-the-ear (BTE) transistor hearing aid showing its triangular-shaped rear profile. It was much thicker at the bottom than at the top.
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| Lower rear view of the Audiotone Model A-28 "Pinal" behind-the-ear (BTE) transistor hearing aid showing battery compartment door (bottom left), microphone/t-coil switch (center right) in the microphone position and the volume control wheel (bottom right).
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| Lower right side view of the Audiotone Model A-28 "Pinal" behind-the-ear (BTE) transistor hearing aid showing the "M" (microphone) and "T" (t-coil) positions for the M/T switch (top) and the name (Audiotone) and model number (A-28) (bottom).
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| Top view of the Audiotone Model A-28 "Pinal" behind-the-ear (BTE) transistor hearing aid showing the front-facing microphone port (top right).
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| Bottom view of the Audiotone Model A-28 "Pinal" behind-the-ear (BTE) transistor hearing aid showing the battery compartment door with the serial number on it (top right) and volume control wheel (bottom right).
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| Close-up view of the opened battery compartment door of the Audiotone Model A-28 "Pinal" behind-the-ear (BTE) transistor hearing aid showing the serial number (6961) on it.
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| View of the opened battery compartment door of the Audiotone Model A-28 "Pinal" behind-the-ear (BTE) transistor hearing aid.
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| View of the battery compartment of the Audiotone Model A-28 "Pinal" behind-the-ear (BTE) transistor hearing aid showing the No. 675 battery in the battery compartment. Hearing aids of this vintage typically used a mercury 675 battery such as the Eveready EP675E.
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