Gem Model 31 Carbon Hearing Aid The Gem Model 31 carbon hearing aid was manufactured by The Gem Ear Phone Co. of New York, NY probably in 1930. It consisted of a microphone, earphone, battery and cords to attach these items together. |  | Click picture for larger view | | |   | | | |
| Front view of the microphone of the Gem Model 31 carbon hearing aid. The microphone grill consisted of 3 concentric circles of small holes—16 holes in the outside ring, 8 in the middle ring and 2 and a small slot in the center. The microphone was 2⅜" (6.0 cm) in diameter and ¾" (1.8 cm) thick. Around the rim of the microphone are the words "The Gem Ear Phone Co., New York". |  | Click picture for larger view | | | |
| Rear view of the Gem Model 31 carbon hearing aid microphone. Near the top are the words, "Made in U.S.A.". At the top of the microphone is a hole for threading a cord through so you could hang the microphone around your neck if so desired. The volume control was the fiber disc on the back. It is shown in the loudest position. A "9" shows in the small hole at the 2 o'clock position. Just below the volume control disc is stamped "GEM 30". Apparently, the same microphone was used for the Gem Model 30 and the Model 31. The main difference was the size of the earphones. |  | Click picture for larger view | | | |
| The Gem Model 31 carbon hearing aid had a "sound perfector" that fitted over the front of the microphone (shown here to the right of the microphone). The "sound perfector" acted like a shield to make the microphone more directional from the front, and thus would enhance the sound of the person to whom you were talking. |  | Click picture for larger view | | | |
| Inside view of the "sound perfector" It was just a hollow chamber that fit to the front of the microphone.
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| When fitted to the Gem Model 31 microphone, the "sound perfector" made the microphone much thicker—1 5/16" (3.4 cm) thick, instead of it's usual ¾" (1.8 cm) thickness. |  | Click picture for larger view | | | |
| Seen from the front, the microphone with the "sound perfector" mounted on it didn't look much different from the front view of the microphone without the "sound perfector" in place. Around the rim of the "sound perfector" are the words, "Gem Ear Phone Co. N.Y." and "Pat. Appl'd For".
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| The earphone cord plugged into the top of the Gem Model 31 carbon hearing aid's microphone. The two jacks and plugs had different sized pins/holes so you couldn't plug them in wrong, thus preserving the proper polarity. |  | Click picture for larger view | | | |
| View of the top of the Gem Model 31 carbon microphone showing the earphone cord plugged into the microphone.
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View of the bottom of the Gem Model 31 carbon microphone showing the battery sockets. Note that the left one is larger than the right on so you couldn't plug the battery in with reversed polarity.
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View of the Gem 31 carbon hearing aid showing how the microphone (left) and the battery (right) fit together when used as a one-piece unit.
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The Gem Model 31 carbon hearing aid used a Gem 1A 3-volt battery.
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| A cool feature of the Gem Model 31 carbon hearing aid was that you could "hide" the battery in your pocket by using the microphone extension cord. This way you wouldn't have the weight of the battery hanging around your neck with the microphone attached. This made the hearing aid into a two-piece unit. The microphone extension cord was about 15" (38.5 cm) long. |  | Click picture for larger view | | | |
View of the Gem 31 carbon hearing aid showing how the microphone extension cord (left) plugged into the battery (right).
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The microphone extension cord plugged into the battery of the Gem 31 carbon hearing aid.
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| The other end of the microphone extension cord plugged into the bottom of the microphone. |  | Click picture for larger view | | | |
| The microphone extension cord shown plugged into the microphone of the Gem Model 31 carbon hearing aid.
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| Front view of the earphone for the Gem Model 31 carbon hearing aid. This earphone was much smaller than was used on the Gem 30 and similar models. It's small size allowed it to be worn on the ear—held there by a wire ear hook. The earphone measured 1 11/16" (4.3 cm) in diameter by ½" (1.3 cm) thick. It only weighed 1.3 oz (38 g).
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Rear view of the Gem Model 31 earphone showing the "on/off" switch, shown here in the "on" position (top).
The model number (GEM 31) is shown stamped into the lower center of the earphone back.
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| Side view of the Gem Model 31 carbon hearing aid earphone showing the wire ear hook. You could also use a headband with this earphone. The hole on the bottom is where the headband (missing) for the earphone snaps in. There is a corresponding hole on the other side of the earphone.
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| The front of the Gem Model 31 carbon hearing aid had a round microphone opening so you could use the hearing aid without taking it out of the carrying case.
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| The Gem Model 31 carbon hearing aid it its carrying case.
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| The Gem Model 31 carbon hearing aid carrying case was finished in black leatherette. The case measured 7½" (19.0 cm) by 3 7/16" (8.7 cm) by 2 13/16" (7.1 cm) high.
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