Sonotone Model 521 Battery Meter
The Sonotone Model 521 Battery Meter was made by the Sonotone
Corporation of Elmsford, NY. It was designed to test both the A
and B batteries in vacuum tube (2-piece) hearing aids made in the late
1930s and the early
1940s. It probably dates to about 1938.
It had a dual range meter.
The 2-pin plug (center) fitted "A" batteries such as the
Sonotone X8000
1˝ volt "A" battery for example, while the 3-pin plug (right) fitted "B" batteries such as the
Zenith Z-30 45
volt "B" battery. Thus the correct scale was automatically selected.
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Close-up of the Sonotone Model 521 battery tester showing the dual-range
meter. The upper scale could test "B" batteries with voltages up to 75
volts. The lower scale could test "A" batteries with voltages up to 5
volts.
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The back of the Sonotone Battery Meter showing the model number "Model
521".
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The Sonotone Model 521 Battery Meter in its original box.
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Outside view of the Sonotone Model 521 Battery Meter box.
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