Sonotone Model 910 Vacuum Tube Hearing Aid The Sonotone model 910 vacuum tube hearing aid was manufactured by Sonotone International, Inc. of Ossining, New York in 1949. The Sonotone model 910 vacuum tube hearing aid weighed 7 oz. with both the "A" and "B" batteries installed. It measured 3 11/16" high x 2 5/16" wide by ⅞" thick (9.4 x 5.9 x 2.2 cm). It contained 3 vacuum tubes. An unusual feature of this hearing aid was that it could use a large external "A" battery for longer life, or a small internal "A" battery for greater portability. |  | Click picture for larger view | | |   | | | |
| Front view of the Sonotone model 910 vacuum tube hearing aid showing the gold-colored microphone grill (top center). |  | Click picture for larger view | | | |
| Rear view of the Sonotone model 910 vacuum tube hearing aid showing the pocket clip (top center) and the battery compartment door (bottom half). The battery compartment door swung up from the bottom. An unusual feature of this hearing aid is that the front and back looked nearly identical. |  | Click picture for larger view | | | |
| Top view of the Sonotone model 910 vacuum tube hearing aid showing the volume control wheel (left), the receiver cord plug (center) and the 3-position on-off lever (right). Note: the reddish "wheel" (right) is just a dummy and doesn't move, only the chrome lever moves. The 3-position on-off switch was something that Sonotone used. There was the "full on" position (shown) (2nd click) and the "bi-focal" position (1st click). In this position it "dimmed out" background sounds for clearer hearing in crowded, noisy places". |  | Click picture for larger view | | | |
| Top view of the Sonotone model 910 vacuum tube hearing aid showing the receiver cord unplugged. |  | Click picture for larger view | | | |
| Left side view of the Sonotone model 910 vacuum tube hearing aid showing the pocket clip (mid right) and the on-off switch (bottom right). |  | Click picture for larger view | | | |
| Bottom view of the Sonotone model 910 vacuum tube hearing aid showing the serial number (167447) (left) and the hole for the external battery cord (mid right). |  | Click picture for larger view | | | |
| View of the empty battery compartment of the Sonotone model 910 vacuum tube hearing aid. |  | Click picture for larger view | | | |
| Close-up view of the bottom of the empty battery compartment of the Sonotone model 910 vacuum tube hearing aid showing the manufacturer (Sonotone) and the model (910). Above this is "Made in U.S.A." and "See patent notice in instruction book". At the top is the polarity arrow pointing to the right (positive terminal). |  | Click picture for larger view | | | |
View of the inside of the battery compartment lid of the Sonotone model 910 vacuum tube hearing aid. It reads, "Remove "A" battery when instrument is not in use" and below that, "Sonotone".
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| View of the battery compartment of the Sonotone model 910 vacuum tube hearing aid showing the Eveready No. 1015E 1˝ volt "A" battery (front) and behind it is the Eveready No. 412E 22˝ volt "B" battery. This was the internal battery arrangement.
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| View of the open battery compartment of the Sonotone model 910 vacuum tube hearing aid showing the external battery arrangement—the large Sonotone X-800 1˝ volt "A" battery (left), the Eveready No. 412E 22˝ volt "B" battery (center) and the Sonotone phantom "A" battery (bottom) connected by a cord to the external "A" battery. The phantom "A" battery was basically a hollow battery shell that connected the two battery terminals to the external battery cord. |  | Click picture for larger view | | | |
| Close-up of the bottom of the Sonotone model 910 vacuum tube hearing aid showing the slot for the external "A" battery cord as seen with the battery compartment door open. |  | Click picture for larger view | | | |
| Close-up of the bottom of the Sonotone model 910 vacuum tube hearing aid showing the hole for the external battery cord to go through as seen when the battery compartment door is closed. |  | Click picture for larger view | | | |
| Outside view of the bottom of the Sonotone model 910 vacuum tube hearing aid showing the external battery cord coming from the bottom of the hearing aid case. |  | Click picture for larger view | | | |
| The external Sonotone X-800 "A" battery was as tall as the hearing aid itself. This is what you saw when the external "A" battery/phantom "A" battery was being used. |  | Click picture for larger view | | | |
| Side view of the Sonotone model 910 vacuum tube hearing aid receiver showing the receiver cord unplugged.
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| Rear view of the Sonotone model 910 vacuum tube hearing aid receiver showing the receiver cord plugged in.
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| Side view of the Sonotone model 910 vacuum tube hearing aid receiver with the ear mold snapped to it.
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| The Sonotone model 910 vacuum tube hearing aid receiver and ear mold shown unsnapped.
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