Sonotone Model 940 Vacuum Tube Hearing Aid The Sonotone Model 940 vacuum tube hearing aid was manufactured by Sonotone International, Inc. of Elmsford, NY in 1950. The Sonotone Model 940 vacuum tube hearing aid weighed 3.8 oz. (106 g) without the batteries. It measured 3⅞" high x 1 7/16" wide by ¾" thick (9.8 x 3.7 x 2.0 cm). It used 3 vacuum tubes. |  | Click picture for larger view | | |   | | | |
| Front view of the Sonotone Model 940 vacuum tube hearing aid showing its design of elegant simplicity. This aid was quite small for a vacuum tube hearing aid. |  | Click picture for larger view | | | |
| Close-up view of the microphone grill of the Sonotone Model 940 vacuum tube hearing aid. The microphone grill consisted of 8 vertical slots behind the gold-colored pocket clip and four short slots on each "shoulder" |  | Click picture for larger view | | | |
| Right side view of the Sonotone Model 940 vacuum tube hearing aid showing the 2-hole jack for the optional external microphone. Note the 4 small slots on the "shoulder" (upper right). These allowed the microphone to pick up sounds from the sides better. There were an additional 4 slots on the other side. |  | Click picture for larger view | | | |
| Top view of the Sonotone Model 940 vacuum tube hearing aid showing the on-off/volume control wheel (center). This was the only control on this aid. Note the "S" (for Sonotone) in the center of the volume control. |  | Click picture for larger view | | | |
| Rear view of the Sonotone Model 940 vacuum tube hearing aid showing the swing up battery compartment door on the bottom half. |  | Click picture for larger view | | | |
| Close-up view of the bottom of the Sonotone Model 940 vacuum tube hearing aid showing the serial number (71016) (left) and the thumb-tab for opening the battery compartment door (center). |  | Click picture for larger view | | | |
| View of the empty battery compartment of the Sonotone Model 940 vacuum tube hearing aid. |  | Click picture for larger view | | | |
| Close-up view of the battery compartment of the Sonotone Model 940 vacuum tube hearing aid showing the 15 volt "B" battery (Eveready No. 504E) (left) and the 1.4 volt mercury "A" battery (Mallory No. RM-1) (right). |  | Click picture for larger view | | | |
| Close-up view of the inside of the lid of the battery compartment of the Sonotone Model 940 vacuum tube hearing aid showing the make (Sonotone) and the model number (940) and the correct placement and polarity of the 2 batteries.. |  | Click picture for larger view | | | |
| Left side view of the Sonotone Model 940 vacuum tube hearing aid showing the receiver cord plugged in.
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| Close-up view of the left side of the Sonotone Model 940 vacuum tube hearing aid showing the receiver cord unplugged. |  | Click picture for larger view | | | |
| Edge view of the receiver and receiver cord plug of the Sonotone Model 940 vacuum tube hearing aid showing the receiver cord unplugged. |  | Click picture for larger view | | | |
| Rear view of the receiver for the Sonotone Model 940 vacuum tube hearing aid showing the receiver cord plugged in. |  | Click picture for larger view | | | |
| Side view of the receiver and ear mold for the Sonotone Model 940 vacuum tube hearing aid showing how they snapped together. |  | Click picture for larger view | | | |
| Front view of the receiver of the Sonotone Model 940 vacuum tube hearing aid showing it unsnapped from the ear mold (left). |  | Click picture for larger view | | | |
| The Sonotone Model 940 vacuum tube hearing aid in its original carry case.
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| View of the inside of the lid of the carry case of the Sonotone Model 940 vacuum tube hearing aid showing the Sonotone inscription "Sonotone" and "The house of hearing". |  | Click picture for larger view | | | |
Outside right front corner view of the Sonotone Model 940 vacuum tube hearing aid carrying case showing the Sonotone name.
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| View of the original carry case of the Sonotone Model 940 vacuum tube hearing aid.
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