Maico Model UD "Atomeer" Vacuum Tube Hearing Aid The Maico model UD (Atomeer) was produced by Maico Electronics, Inc. of Minneapolis, MN in 1947. The name "Maico" was derived from the initials of the Medical Acoustic Instrument Company. It was a 3 vacuum tube one piece model measuring 4⅝” by 2˝ by 1”. It weighed 7˝ oz. with batteries. |  | Click picture for larger view | | |   | | |
| The volume control was in the top left corner and the on-off/tone control (3 tone selections) was on the top right corner. |  | Click picture for larger view | | | |
| A close-up of the front of the circuit board showing the 3 tubes (top left and top right sides and bottom left) and the microphone in the middle. |  | Click picture for larger view | | | |
| A close-up of the rear of the circuit board. |  | Click picture for larger view | | | |
| The Maico Model UD from the rear showing the battery compartment. A round mercury RM-4 "A" battery fitted in the bottom right corner, while a Model 413E 30 volt "B" battery fitted in the space on the left.
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