Zenith Hearing Aid Tester (Battery Tester)
This Zenith dual-scale battery meter was a special
type of battery tester used in the late 1930s and up to about 1947 to test
the A and B
batteries in two-piece vacuum-tube hearing aids.
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This tester had 2 scales—the upper one ranging from 0 to 50 volts for
testing "B" batteries, and the lower one ranging from 0 to 2 volts for testing
"A" batteries. |
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This meter was one of the easiest to use. You couldn't get the polarity
wrong, nor could you accidentally try to check a high voltage "B"
battery on the "A" battery scale (and burn out the meter). "B"
batteries of the day had 3-hole jacks arranged in a triangular fashion
which fit the 3 prongs of the "B" battery side of the meter (left),
while "A" batteries had 2 hole jacks that fit the 2 prongs of the "A"
battery side of the meter (right). |
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Top view of "A"
battery (left) showing the 2-hole jack into which the 2 prongs of the
"A" battery side of the tester (right) fit.
Note that the holes of the "A" battery jack and prongs of
the "A" battery tester were of different sizes so
you couldn't accidentally plug the meter in with positive and negative terminals reversed.
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The Zenith hearing aid tester plugged into the 2-prong jack of an "A"
battery. |
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Top view of a "B"
battery (left) showing the 3-hole jack into which the 3 prongs of the
"B" battery side of the tester (right) fit.
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The Zenith hearing aid tester plugged into the 3-prong jack of a "B"
battery. |
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Rear view of the Zenith Hearing Aid Tester. The inscription on the
back reads, "Made in U.S.A. Pat'd. Oct. 3, 1916.
It is obvious that the patent refers to the meter workings and not to
this particular battery tester as as 3-hole batteries were not made
until about 1937. This style of battery became obsolete around
1947 when hearing aid manufacturers changed from external to internal
batteries.
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