Sonotone Model 977 Vacuum Tube Hearing Aid The Sonotone Model 977 vacuum tube hearing aid was manufactured by Sonotone International, Inc. of Elmsford, NY in 1951. The Sonotone Model 977 vacuum tube hearing aid weighed 4.9 oz. (140 g) without the batteries. It measured 3 7/16" high x 2⅛" wide by ⅞" thick (8.8 x 5.4 x 2.2 cm). It used 3 vacuum tubes. |  | Click picture for larger view | | |   | | | |
Front view of the Sonotone Model 977 vacuum tube hearing aid. The silver-colored metal case had a grey/blue plastic insert (center). Note the Sonotone "S" at the top of the gold-colored pocket clip (top center).
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| Top view of the Sonotone Model 977 vacuum tube hearing aid showing the 3-position on-off switch (left), volume control (center) and the receiver cord jack with the receiver cord plugged into it (right). The 3-position on-off switch was something that Sonotone used. There was the "full on" position (shown) (2nd click) and the "bi-focal" position (1st click). In this position it "dimmed out" background sounds for clearer hearing in crowded, noisy places". |  | Click picture for larger view | | | |
| Close-up view of the top right corner of the Sonotone Model 977 vacuum tube hearing aid showing the recessed two-pronged receiver cord jack and receiver cord plug. |  | Click picture for larger view | | | |
| Close-up view of the microphone grill of the Sonotone Model 977 vacuum tube hearing aid. The grill consisted of 2 square holes hidden beneath the pocket clip. |  | Click picture for larger view | | | |
| Rear view of the Sonotone Model 977 vacuum tube hearing aid. The whole back comprised the battery compartment door. It swung out to the left. |  | Click picture for larger view | | | |
| Left side view of the Sonotone Model 977 vacuum tube hearing aid showing the release button to open the battery door (center) and the 3-hole jack—probably for an external microphone (right of center). |  | Click picture for larger view | | | |
| View of the right side of the Sonotone Model 977 vacuum tube hearing aid showing the battery compartment door hinge. |  | Click picture for larger view | | | |
| Inside view of the empty battery compartment of the Sonotone Model 977 vacuum tube hearing aid with the battery compartment door swung out to the left. It only swung out 90°. |  | Click picture for larger view | | | |
| View of the inside of the lid of the battery compartment of the Sonotone Model 977 vacuum tube hearing aid (left) showing the make (Sonotone) and the model number (977). Below that is "Sonotone Corporation/ Elmsford, New York/Made in U.S.A." At the bottom is "See patent notice in instruction book". On the right is the battery compartment showing the 30 volt "B" battery (Eveready No. 507E) (center) and the 1.4 volt mercury "A" battery (Mallory No. RM-1) (bottom right). |  | Click picture for larger view | | | |
| Close-up view of the bottom right corner of the Sonotone Model 977 vacuum tube hearing aid battery compartment showing the serial number (531109) (left) and the "A" battery. (right) |  | Click picture for larger view | | | |
| Inside upper view of the battery compartment of the Sonotone Model 977 vacuum tube hearing aid showing the low cut (1-2) adjustment (right) The low-cut filter helped cut out the louder low-frequency sounds if they were bothersome. |  | Click picture for larger view | | | |
| Side view of the low-cut filter of the Sonotone Model 977 vacuum tube hearing aid shown in the "2" position. |  | Click picture for larger view | | | |
| Inside lower view of the Sonotone Model 977 vacuum tube hearing aid showing the high cut (A-B) adjustment (left) and the 3-position "cushion" adjustment (center). The high-cut filter cut out the sharper high-frequency sounds if they were bothersome. It is unknown exactly what the "cushion" adjustment was for. |  | Click picture for larger view | | | |
| Edge view of the receiver and receiver cord plug of the Sonotone Model 977 vacuum tube hearing aid showing the receiver cord unplugged. Note the unusually long pins on the receiver cord plug. |  | Click picture for larger view | | | |
| Rear view of the receiver for the Sonotone Model 977 vacuum tube hearing aid showing the receiver cord plugged in. |  | Click picture for larger view | | | |
| Side view of the receiver and ear mold for the Sonotone Model 977 vacuum tube hearing aid showing how they snapped together. |  | Click picture for larger view | | | |
| Front view of the receiver of the Sonotone Model 977 vacuum tube hearing aid showing it unsnapped from the ear mold (left). This hearing aid was donated by Ruth Bott in memory of her mother, Helen York of White Plains, NY who wore it.
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