Gem Model 30 Standard "2" Carbon Hearing Aid The Gem Model 30 Standard "2" carbon hearing aid was manufactured by The Gem Ear Phone Co. of New York, NY around 1930. There were a number of early Gem carbon hearing aids. Since Gem didn't put model numbers on these aids, and since there are few, if any, records describing each model, it is impossible to know for sure which model is which. As a result, to differentiate different similar unmarked models in the museum, I have simply given a serial number in quotes (e.g. "2") to these unknown models. Thus this Gem carbon hearing aid is "2" version of what I think is the Gem Model 30 Standard carbon hearing aid.
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| The Gem 30 Standard "2" could also be configured with a microphone-battery extension cord so the battery could be separate from the microphone. That way the microphone could be worn around the neck on a lanyard, while the heavy battery was carried in a pocket. This hearing aid was a pretty basic unit consisting of a microphone and an earphone connected by a single cord (unless you were also using the battery extension cord). This hearing aid weighed 12.9 oz. (366 g) with the battery and 5.4 oz. (154 g) without the battery).
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| Front view of the microphone of the Gem Model 30 Standard "2" carbon hearing aid. The microphone grill consisted of two concentric rows of holes—16 holes in the outer row and 8 holes in the inner row. The center was a slot. The microphone measured 2⅜" in diameter by 13/16" thick (6.0 x 2.1 cm). Around the rim of the microphone are the words "The Gem Ear Phone Co." and "New York". |  | Click picture for larger view | | | |
| Rear view of the microphone of the Gem Model 30 Standard "2" carbon hearing aid showing the fiber volume control (black thumb wheel in center). Notice the small hole at the 12 o'clock position showing the volume level (5 in this case). Volume ranged from 1 to 9. At the top of the volume control is a hole for threading a lanyard through so you could hang the microphone around your neck if so desired. Note the words "Made in U.S.A." just above the volume control wheel. |  | Click picture for larger view | | | |
| Side view of the microphone of the Gem Model 30 Standard "2" carbon hearing aid showing the raised black fiber volume control wheel. It had a serrated edge for ease of turning.
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| Close-up view of the Gem Model 30 Standard "2" carbon hearing aid battery (left) and microphone (right). The pins are of slightly different size (the left pin is larger) so you could only plug them together the right way ensuring the correct polarity. This hearing aid used a 3-volt carbon-zinc Gem 1A battery (left).
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| Close-up view of the Gem Model 30 Standard "2" carbon hearing aid showing the microphone plugged directly onto the battery terminals.
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| Instead of plugging the microphone directly onto the battery terminals, you could use the 16" (40.3 cm) extension cord so the battery could be carried in a pocket. In this case you'd have to wear the microphone around your neck to keep it relatively vertical so it would work. (Carbon microphones won't work when laying flat as the carbon shot can't touch both terminals at the same time when laying flat.)
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| Close-up view of the battery of the Gem Model 30 Standard "2" carbon hearing aid showing the battery pins and the female ends of the extension cord.
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| Close-up view of the battery of the Gem Model 30 Standard "2" carbon hearing aid showing the extension cord plugged onto the battery terminals.
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Close-up view of the microphone of the Gem Model 30 Standard "2" carbon hearing aid showing the female microphone jacks and the male ends of the extension cord. The left pin and jack are larger than the right ones.
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Close-up view of the microphone of the Gem Model 30 Standard "2" carbon hearing aid showing the male extension cord pins plugged into the microphone jacks.
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Side view of the Gem Model 30 Standard "2" carbon hearing aid. Notice that the prongs on the battery are set near the back (right side) instead of in the center of the top of the battery as was more common. This provided better stability for the hearing aid since the microphone was "front heavy". It also provided for a sleeker-looking hearing aid.
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| Front view of the earphone of the Gem Model 30 Standard "2" carbon hearing aid. The earphone measured 2 1/16" in diameter by 13/16" thick (5.2 x 2.0 cm).
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| Rear view of the earphone of the Gem Model 30 Standard "2" carbon hearing aid. Note the "On-Off" switch at the top.
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| Close-up view of the Gem Model 30 Standard "2" carbon hearing aid earphone showing the on-off switch on the side (top) with the "On" and "Off" positions shown on the back, here shown in the "off" position. The earphone was held in place by a headband the snapped into two small holes in the sides of the earphone. You can see one of the holes on the side of the earphone directly above the "O" of the "On".
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| View of the headband of the Gem Model 30 Standard "2" carbon hearing aid with the earphone snapped in place on the gimble bracket.
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| Inside view of the Gem Model 30 Standard "2" carbon hearing aid packed into its carrying case.
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| View of the top center of the lid of the carrying case for the Gem Model 30 Standard "2" carbon hearing aid showing the inscription, "The Gem Earphone Co." and "New York".
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| Outside view of the carrying case for the Gem Model 30 Standard "2" carbon hearing aid. It was finished in black leatherette. The case measured 7⅜" by 2 13/16" by 2⅞" deep (18.6 x 7.1 x 7.3 cm).
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