Siemens Model 23 Carbon Hearing Aid The Siemens Model 23 carbon hearing aid was made by Siemens & Halske A. G. of Germany around 1925. It appears to be the quad-microphone version of the double-microphone Siemens M-22 carbon hearing aid. Unfortunately, the battery cord/ earphone cord and receiver/earmold are missing, but it is highly likely that these items are quite similar to these same items on the Siemens Model M-22 which you can see here. It probably also used the same battery, a 4½ volt Fortiphone No. 3-S battery.
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| The front of the Siemens Model 23 carbon hearing aid quad-microphone. Each microphone grill consisted of an outer circle of 12 diamond-shaped cut-outs and an inner row of alternating diamond-shaped cut-outs and small circles. The quad carbon microphone assembly measured 4¼" square x ⅞" thick. It weighed 7.2 oz. Note the leather button-hole (top). This way the microphone could be attached to any button on the wearer's clothes. Alternately, a ribbon could be threaded through the button hole so the hearing aid could be worn on a lanyard around the wearer's neck.
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| Rear view of Siemens Model 23 carbon hearing aid microphone. Engraved on the back just below the leather button hole are the words "Siemens & Halske A. G. Germany"
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| Side view of Siemens Model 23 carbon hearing aid microphone showing the 2 jacks for the battery/earphone cord plugs. Quad-microphones provided more amplification that single or double microphones. Hence, they were the "power aids" of the day.
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| Side view of the Siemens Model 23 carbon hearing aid microphone showing the foot folded in place for use when wearing it on a lanyard or fastened to a button.
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| Bottom view of the Siemens Model 23 carbon hearing aid microphone showing the "foot" swung out so it could stand upright on a table instead of laying flat (see top picture). It is easy to forget that carbon microphones only worked when held vertically. When laid down, the carbon shot didn't touch both contacts on the microphone. Hence no current flowed and the hearing aid didn't work.
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