Body-Style Transistor Hearing Aids—General Information
While the vacuum tube, which had been
employed in hearing aids since the early 1920s, was a major advance in
improving the amount of amplification available in hearing aids, further
miniaturization from that achieved by 1950 was not possible because of
the need for two relatively large batteries to power the hearing aids.
This changed when the people at the Bell
Labs invented the transistor in 1948. Hearing aid manufacturers quickly
realized that the transistor represented the future of hearing aids. The
transistor eliminated the need for the "A" battery to power the
filaments of the vacuum tubes, and the "B" battery to power their plates.
Furthermore, the lower operating voltage required by transistors over
that of vacuum tubes meant that a single smaller battery was all that
was required.
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Click picture for larger view |
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Example of One of the More Unusual
(Pen-Shaped) Body-Style Transistor Hearing Aids
in the Museum
Click on the "Transistor (Body)"
button
(on the
left) to see the details
of this and
other body-style
transistor hearing aids. |
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The First Step—Hybrid Vacuum Tube/ Transistor Hearing Aids
This changed when the people at the Bell
Labs invented the transistor in 1948. Hearing aid manufacturers quickly
realized that the transistor represented the future of hearing aids.
In fact, hearing aids were the first commercial application to use transistors.
By substituting a transistor for one of
the three vacuum tubes, filament current drain was reduced by 1/3 resulting in
slightly longer battery life and thus reduced costs to the user.
Hybrid
hearing aids were only produced for about a year before fully transistorized
hearing aids took over the market. They are now relatively rare
to find.
The first hearing aid using a transistor, the Sonotone Model 1010,
reached the market in December 1952. It
used two vacuum tubes, plus one transistor
in the output stage.
A few other manufacturers quickly followed suit with similar
hybrid models. These included:
Acousticon (models A-300 & A-310), Audiotone (model 15),
Aurex (model T-2),
Bonochord (Transitron M-30),
Dahlberg (model D-5),
Danavox (models 520 & 527),
Fortiphone (model 40),
Omnitone (model T-1),
Otarion
(models C-15, C30 & F-22), Siemens (Delta), and
Telex (model 954).
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Click picture for larger view |
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Example of a Hybrid Vacuum Tube/Transistor Hearing Aid
Click on the "Transistor
(Body)"
button
(on the
left) to see the details
of this and
other body-style
transistor hearing aids. |
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All Transistor Hearing Aids
All-transistor hearing aids first hit
the market in 1953. The demise of the vacuum tube quickly followed.
Most hearing aid manufacturers quickly realized the benefits for both
the consumer and the manufacturer.
This remarkable device with its small
size, even in comparison with the miniature hearing aid vacuum tubes,
and the elimination of one of the batteries in hearing aids allowed much
greater reductions in size of hearing aids to follow in the 1950s and
1960s.
This category in the museum includes samples of transistor body aids
from 1953 through to the 1980s when ear level hearing aids had become
powerful enough to make body aids virtually obsolete except for the most
severe hearing losses.
If you want to learn more about the transistor and its use in hearing aids check
out:
Bob
McGarrah's Virtual Transistor Museum and History Website
and
The CK722
Classic Germanium Transistor Museum |
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Click picture for larger view |
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Example of a Body-Style Transistor Hearing Aid
Click on the "Transistor (Body)"
button
(on the
left) to see the details
of this and
other body-style
transistor hearing aids.
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(If a larger picture doesn't appear, you may have to
turn your pop-up blocker off)
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