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CIA Maico Mic Bugs
The device consists of a black plastic body and has a stainless steel
front panel, embossed with the name 'MAICO'.
At the left side is a
socket for an earpiece.
At the right
side is the volume knob with built-in on/off switch.
It is powered by an R-401 mercury battery of 1.4V, 1 that should be
installed behind a hinged panel at the back. 2
The device is basically a standard Maico Model R from which the internal
microphone is removed and a 3 mm jack socket has been added at the top.
The metal clip, that was used to attach the device to the clothing,
has also been removed.
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It is likely that the Maico Model R was modified for CIA use in 1954 or
shortly thereafter, as the Model R was succeeded in 1955 by newer designs,
such as the models S, V and W [2].
It is known from an internal CIA memorandum, that by July 1957,
the device was internally referred to as 'the standard Maico probe' [3].
It is also known from
surviving CIA Operating Instructions [A],
that the device had the CIA designator Amplifier #216, and that it was
used to amplify the sound picked up by Probe #6143. The latter is currently
unknown, but was probably a condenser microphone.
Maico is a commercial hearing aid brand, founded in 1937 in Minneapolis
(Minnesota, USA) by Leland A. Watson.
It was one of the first companies in the world to introduce an
all-transistor hearing aid in 1953, shortly after the invention of
the transistor (1947). 3
The Model R was one of its successors, and was built around three CK718 transistors, made by Raytheon in the US [4].
Maico Diagnostics
still exists today, and has offices in Minneapolis (USA) and
Berlin (Germany).
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Ray-O-Vac R-401, Beltone BP401R, Duracell RM-401H, Eveready E401E,
Zenith ZM401.
Note that mercury batteries are no longer produced today, because of the
environmental impact of mercury.
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It should be noted that the battery lid is (manually) engraved with the
text Mallory TR-152 2.5V, which is almost twice the required voltage
of 1.4V. It is possible that the CIA used the higher voltage.
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Although the principle of the transistor was invented in 1947 at
Bell Labs (USA), it was first produced
in large quantities by Raytheon (USA) in 1952 – especially for use in
hearing aids – followed in 1954 by Texas Instruments (USA) and later
Sony (Japan) for use in consumer appliances [4][5].
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The Maico Model R consists of a black plastic body with a stainless
steel front panel, that is held in place by three screws: two at the
sides towards the top, and one at the bottom. After removing
these screws — don't lose them — the
front panel can be lifted off, and the
interior is exposed.
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Towards the bottom is a battery compartment that accepts a 1.4V type 401
mercury battery, to be inserted behind a
hinged lid at the rear
of the device. The rest of the case is filled with a brown pertinax
printed circuit board (PCB) on which the electronic components are fitted.
The volume control knob can be operated from the side.
The empty space at the centre of the PCB
is where the internal microphone was originally fitted.
It was removed by the CIA and replaced by a 3 mm jack receptacle,
in order to use it as a pre-amplifier for external (probe) microphones.
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The circuit consists of three amplifier stages, coupled by means
of transformers.
Each stage is built around a CK718 transistor, that was first made in large
quantities in 1952 by Raytheon (US).
They were developed especially for
maintaining Raytheon's dominant position in the hearing aid industry,
for which they had previously produced special subminiature vaccum tubes.
The CK718 is a Germanium Alloy Junction Transistor [4].
The Maico Model R was in production until 1955.
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© Crypto Museum. Created: Saturday 19 September 2020. Last changed: Thursday, 20 April 2023 - 13:52 CET.
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