Acousticon Model SRD Carbon Hearing Aid The Acousticon model SRD was a dual microphone carbon hearing aid manufactured between 1910 and 1928 by the General Acoustic Company, which later became Dictograph Products, Inc.
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| Front view of the Acousticon SRD showing the double carbon microphone. Note that the microphone grill consists of 8 slots for each microphone. This carbon microphone measured 5⅞" by 3⅜" by 15/16" thick. |  | Click picture for larger view | | | |
| The back of the Acousticon SRD carbon microphone. The volume control is to the left. |  | Click picture for larger view | | | |
| Close-up of the back of the Acousticon SRB carbon microphone showing the model number (SRB) (upper left) and the pocket clip (center). |  | Click picture for larger view | | | |
Close-up of the 6-step volume control. Soft is to the left and loud to the right.
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| Bottom view of the Acousticon Model SRD microphone showing the battery plugs (left) and the battery jacks on the bottom of the carbon microphone. The microphone plugs and jacks are all the same size no can be plugged in either way. |  | Click picture for larger view | | | |
| The Acousticon Model SRD used a 3-volt carbon-zinc battery. The battery cable plugged into the jacks on the top of the battery. Note the two sizes of the plugs and jacks so you couldn't plug them in the wrong way. The battery shown here is an Acousticon No. 5 Hearing Aid battery. |  | Click picture for larger view | | | |
| The earphone for the Acousticon Model SRD could be hand-held. The handle snapped into two depressions on each side of the earphone. |  | Click picture for larger view | | | |
| The handle extended to make it more comfortable to hold up to your ear. |  | Click picture for larger view | | | |
| The Acousticon Model SRD also came with a headband that snapped into the two depressions on each side of the earphone. This made for hands-free listening. |  | Click picture for larger view | | | |
| Bottom view of the Acousticon Model SRD earphone showing the earphone plugs (left) and the earphone jacks on the bottom of the earphone. The two plugs are slightly different in size as are the two jacks so you have to plug them in the right way. Note the "On" and "Off" markings to the left and right of the earphone jacks respectively, and the on-off switch shown in the off position (just visible below the right earphone jack). |  | Click picture for larger view | | | |
| The back of the Acousticon Model SRD earphone showing the on-off switch immediately above the earphone plugs. It is in the off position. |  | Click picture for larger view | | | |
| The Acousticon Model SRD in its carrying case. |  | Click picture for larger view | | | |
| The carrying case for the Acousticon Model SRD carbon hearing aid.
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