Vacolite Model D Vacuum Tube Hearing Aid The Vacolite Model D vacuum tube hearing aid was manufactured by the Vacolite Company of Dallas, TX in 1941. The Model D measured 4¾” by 2⅜” by 1” thick and weighed 7¾ oz. without the batteries. |  | Click picture for larger view | | |  | | |
| The Vacolite Model D was a 2-piece, 2 vacuum-tube model. It required two batteries, a 1½ volt "A" battery such as this Zenith A battery and a 33 volt "B" battery (that would have looked similar and had the same plug configuration as this Zenith Z-30 "B" battery, although this was a 45 volt battery).
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| Front view of the Vacolite Model D showing the microphone grill. It was arranged in two concentric circles of 10 and 4 holes. This hearing aid used a crystal microphone. |  | Click picture for larger view | | | |
| Rear view of the Vacolite Model D hearing aid showing the pocket clip (upper center). In the center of the back is inscribed: Made by
Vacolite Company
Dallas, Texas
Model D |  | Click picture for larger view | | | |
| Top view of the Vacolite Model D showing the volume control. This was the only control on this hearing aid. There doesn't appear to have been an on-off switch (at least, you can't feel the volume control snap to the off position). |  | Click picture for larger view | | | |
| Bottom view of the Vacolite Model D showing how the battery cord plug fits into the bottom of the hearing aid. |  | Click picture for larger view | | | |
| Bottom view of the Vacolite Model D showing how the battery cord plug and the jack in the bottom of the hearing aid. |  | Click picture for larger view | | | |
| Close-up of the 3-pronged "B" battery plug (left) and the 2-pronged "A" battery plug (right). |  | Click picture for larger view | | | |
| Back view of the crystal receiver of the Vacolite Model D showing how the receiver cord plug fits together. Piezo-electric crystal receivers were thinner, but bigger in diameter than the more common dynamic receivers. This one measured 1" in diameter. This receiver was made by by The Brush Development Company of Cleveland, OH. Brush applied for a US patent on March 20, 1939 and received Patent No. 2,261,979 on November 11, 1941. In addition to Vacolite, crystal receivers were used by other hearing aid manufacturers such as Beltone and Maico for hearing aids made in the 1940s.
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| Back view of the crystal receiver of the Vacolite Model D showing how the receiver cord plug slid from the right into grooves on the receiver, rather than plugging in as was more common. |  | Click picture for larger view | | | |
| The receiver (left) and the ear mold (right) of the Vacolite Model D snapped apart. |  | Click picture for larger view | | |
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