Acousticon A-90M (Imperial) Vacuum Tube Hearing Aid The Acousticon A-90M (Imperial) hearing aid was produced by Dictograph Products, Inc. of New York in 1948. It looked much the same as the 1-piece A-90 except it was finished in gold anodized aluminum rather than with silver-colored polished aluminum. The left 2/3 of the front of the case was finished with light brown enamel. The hearing aid measured 4” by 2⅜” by ⅞”. |  | Click picture for larger view | | |   | | | |
| The Acousticon A-90M featured the same controls as the 1-piece Acousticon A-90 with the volume control at the top left corner, and the microphone on the front behind the grill/logo at the top right. Note that the microphone grill is not set flush with the front as was the grill of the 1-piece Acousticon A-90, but is recessed a bit. |  | Click picture for larger view | | | |
| Left side view of the Acousticon A-90M showing the 4 position tone control. The serial number (1T571) is to the right of the tone control. Note the clip to hold the hearing aid in place on the clothing (bottom left). |  | Click picture for larger view | | | |
| The Acousticon A-90M was powered by internal batteries—a 1.4 volt No. 4 (equivalent to the Mallory RM-4) mercury "A" battery (bottom left), or in some early? versions of this hearing aid, it used the thinner 4Z "A" battery, and a 15 volt Eveready 411E "B" battery (bottom right). |  | Click picture for larger view | | | |
| One puzzling thing about the Acousticon A-90M is that some early? versions of this model did not use the Mallory RM-4 sized "A" battery like the version shown in the above picture did, but used a rare thinner battery called the 4Z like this version did. |  | Click picture for larger view | | | |
| In this particular hearing aid, the Mallory RM-4 battery just won't fit. Also puzzling is that the cases in both these hearing aids are the same thickness—so why the thinner battery in one and a thicker battery in the other? |  | Click picture for larger view | | | |
| The Mallory RM-4 battery (left) in comparison to the 4Z battery (right). When you compare the two you can see why the RM-4 won't fit in this hearing aid. |  | Click picture for larger view | | | |
| Another feature of some versions of the A-90M was the capability to attach the Acousticon Radion radio tuner to the side of the hearing aid, thus turning the hearing aid into a personal AM radio for the user. Note the two holes on the right side for the pins of the Radion to attach/connect to. |  | Click picture for larger view | | | |
| Not all Acousticon A-90M hearing aids had the above feature of the contacts for the Radion. The picture to the right shows the hearing aid that used the 4Z "A" battery. It has no holes for attaching the Radion. |  | Click picture for larger view | | | |
| The Acousticon A-90M with the Radion attached to the right side of the hearing aid. Click here for more information on the Acousticon Radion. |  | Click picture for larger view | | | |
| Some of the Acousticon A-90M hearing aids did not have a receiver cord with attached plug like the above picture does. Earlier versions of the Acousticon A-90M had the receiver cord terminate with pins. |  | Click picture for larger view | | | |
| "Humidrier" for the Acousticon A-90M. This was used to keep moisture out of the electronics. The porous cloth "basket" was lifted out and a drying agent was put in the bottom of the "Humidrier" Then the "basket" was replaced and the hearing aid placed in the "basket" to dry out. |  | Click picture for larger view | | | |
| The Acousticon A-90M in the "Humidrier". The "Humidrier" measured 6½" x 4¾" x 2¼".
|  | Click picture for larger view | | |
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