Unknown Make (XX1) Transistor (Body) Hearing Aid
The manufacturer of this 3-transistor hearing aid is unknown, but it
is almost certainly of European origin, perhaps Audium B.V. of the
Netherlands (here referred to as the Unknown Model XX1.)
It was made between 1954 and 1957, most likely in 1955.
The Model XX1 hearing aid measured
2⅝" x 1 11/16" x 1" (6.6 x 4.2 x 2.5 cm)
and weighed 3.2 oz (90 g) without the battery. It used three
transistors.
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Front view of the Model XX1 transistor hearing aid showing its unique
elegant guilloche enameled front. Since enamel was often done over
silver, the front half of the case is made of silver, while the back
half is chrome.
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Close-up view of the upper front of the Model XX1 transistor hearing aid showing the
intricate guilloche pattern on this hearing aid.
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Top view of the Model XX1 transistor hearing aid showing the 2-hole
receiver cord jack (left), the battery compartment latching clip
(center) and the on-off/volume control wheel (right). Note: this aid
does not have a microphone grill or microphone port. As near as we
can tell, the sound reached the microphone via the space around the
volume control wheel.
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View of the top left corner of the Model XX1 transistor hearing aid showing the
unusual rotary switch shown here in the "1" position (lower left).
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View of the top left corner of the Model XX1 transistor hearing aid showing the
rotary switch in the "2" position (lower left). It is not known what
this switch was for.
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View of the left side of the Model XX1 transistor hearing aid showing
the "1-2" switch (left) and the word "Silver" (upper center). The upper
half of the case is silver and the lower part is covered in chrome. |
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View of the right side of the Model XX1 transistor hearing aid
showing the volume control wheel (left).
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View of the back of the Model XX1 transistor hearing aid showing the
pocket clip (upper center). The whole back of this aid swung down to
reveal the battery compartment.
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Bottom view of the Model XX1 transistor hearing aid showing the hinge
for the swing-down battery
door.
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View of the back of the Model XX1 transistor hearing aid with the
battery compartment door swung down showing the empty battery
compartment (bottom left) and the serial number (17367) above it.
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View of the inside of the battery compartment lid of the Model XX1
transistor hearing aid showing how to correctly place the RM1 battery in
the battery compartment.
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Close-up view of the empty battery compartment of the Model XX1
transistor hearing aid. The plastic tab (bottom) made it easy to pull
out the battery. |
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Close-up view of the battery compartment of the Model XX1 transistor
hearing aid showing the 1.4 volt mercury RM1 battery in place such as
this
Mallory RM1 battery. |
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Inside view of the Model XX1 transistor hearing aid showing the
microphone (round disc center) and the 3 tube-shaped transistors—one
upper right and two lower left. |
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Close-up of the inside of the Model XX1 transistor hearing aid showing
the Mullard OC70 transistor (above) and the OC71 transistor (below).
The OC71 transistor has "Made in Holland" on its back side. Thus this
hearing aid may have been made in Holland. Most Mullard transistors were
made in England. Both of these transistors were developed by Mullard
in 1954. |
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Close-up of the top right inside corner of the Model XX1 transistor
hearing aid showing the Mullard OC70 transistor placed there. |
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Inside view of the case of the Model XX1 transistor hearing aid
showing its repair history with two sets of repairs done in 1964.
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