Sonotone Model 79 Behind-the-Ear (BTE) Transistor Hearing Aid The Sonotone Model 79 behind-the-ear hearing aid was manufactured by Sonotone International, Inc. of New York in June, 1955. Not only was it Sonotone's first behind-the-ear (BTE) hearing aid, it was the very first BTE hearing aid ever made by any hearing aid manufacturer as near as we can tell! It contained 3 transistors and weighed a hefty 0.8 oz. (24 g) without the battery. It measured 1⅞" x 1¼" x ⅝" (4.7 x 3.1 x 1.5 cm). |  | Click picture for larger view | | |  | | | |
| Front view of the Sonotone Model 79 BTE hearing aid showing the receiver (left), receiver cord and dark brown hearing aid (right).
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| Close-up view of the upper side of the Sonotone Model 79 BTE hearing aid showing the microphone grill which consisted of four rows of 3 small squares. |  | Click picture for larger view | | | |
| Rear view of the Sonotone Model 79 BTE hearing aid showing just how thick this hearing aid was. The battery compartment door is on the left. |  | Click picture for larger view | | | |
| Side view of the Sonotone Model 79 BTE hearing aid showing the volume control/on-off switch (lower center). This was the only control on this hearing aid. |  | Click picture for larger view | | | |
Rear view of the Sonotone Model 79 BTE hearing aid. The name and model number are inscribed at the top.
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| Close-up view of the upper rear of the Sonotone Model 79 BTE hearing aid showing the model number at the top (79) and below it the manufacturer's name (Sonotone) and location (Elmsford N.Y. U.S.A.). |  | Click picture for larger view | | | |
| Close-up view of the front of the Sonotone Model 79 BTE hearing aid showing the receiver cord jack. Note that this jack has some unusual features. First, the holes are square rather than round; they are of two sizes—the larger hole at the back and the smaller one at the front; and the socket is a trapezoid shape. |  | Click picture for larger view | | | |
| Close-up view of the front of the Sonotone Model 79 BTE hearing aid showing the jack housing and receiver cord plug (shown unplugged). It was very unusual that the housing protruded out against the ear like it does. Another very unusual feature is the there was a jack at each end of the jack housing so you could plug the receiver cord in from the top (as shown) or from the bottom.
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| Side view of the Sonotone Model 79 BTE hearing aid showing the receiver cord plugged into the top jack. The reason for the two jacks is so the same hearing aid could be worn on either ear and still have the microphone facing out. This was a rather ingenious solution. Note that in this picture, it is configured for the left ear (plugged into the top). You can see the microphone grill is at the top and battery compartment door at the bottom.
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| Side view of the Sonotone Model 79 BTE hearing aid showing the receiver cord plugged into the bottom jack. Note this now the microphone grill is at the bottom and the battery compartment door is at the top. This is the configuration for the right ear. With the volume control in the middle it didn't matter which way was up although you had to remember that to increase the volume you turned the control down if wearing it on the left ear and turned it up if wearing it on the right ear. |  | Click picture for larger view | | | |
| Close-up side view of the receiver and receiver cord plug of the Sonotone Model 79 BTE hearing aid. Note the trapezoid shape of the plug so it would fit into the socket on the hearing aid. |  | Click picture for larger view | | | |
| Side view of the receiver of the Sonotone Model 79 BTE hearing aid showing the receiver cord unplugged. Note the different sized pins and holes—the larger on the left and smaller on the right. |  | Click picture for larger view | | | |
| Close-up view of the receiver of the Sonotone Model 79 BTE hearing aid showing the receiver cord plugged into the receiver. |  | Click picture for larger view | | | |
| Rear view of the receiver of the Sonotone Model 79 BTE hearing aid with the receiver cord plugged in. This receiver was smaller than normal receivers of the time, measuring just ⅝" (1.6 cm) in diameter rather than the more common 13/16" (2.1 cm).
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| Front view of the receiver of the Sonotone Model 79 BTE hearing aid with the receiver cord plugged in. Note that the nubbin in the center of the receiver (where the ear mold snapped on) was much smaller than normal so ear molds made to fit most receivers wouldn't fit on this receiver.
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| Rear bottom view of the Sonotone Model 79 BTE hearing aid showing the battery compartment door ajar. |  | Click picture for larger view | | | |
| Rear bottom view of the Sonotone Model 79 BTE hearing aid showing how the battery compartment door swunp up from the bottom. |  | Click picture for larger view | | | |
| Rear bottom view of the Sonotone Model 79 BTE hearing aid showing a 625 mercury battery in the battery compartment door. The negative terminal faces up. |  | Click picture for larger view | | | |
| Close-up view of the battery compartment door of the Sonotone Model 79 BTE hearing aid showing the No. 625 battery in place. This battery was quite a bit larger than the 675 hearing aid batteries used a few years later. |  | Click picture for larger view | | | |
| Side by side comparison of the size of the Sonotone Model 79 BTE hearing aid and a modern BTE aid (2014 Liberty aid). Aren't you glad hearing aids have gotten smaller? |  | Click picture for larger view | | | |
Side by side comparison of the thickness of the Sonotone Model 79 BTE hearing aid and a modern BTE aid (2014 Liberty aid). What a difference!
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| The Sonotone Model 79 BTE hearing aid actually hung a bit below and behind the ear as shown when worn by "dummy" on the right ear. Very visible! |  | Click picture for larger view | | | |
| In contrast, a modern 2014 model Liberty BTE aid appears almost invisible when worn on the same dummy. You can just see it stick out a bit between 9:00 and 10:00 o'clock. Almost invisible.
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