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Concealed microphone
MM-61 is a dynamic microphone,
concealed as a foutain pen,
manufactured from 1962 onwards by
Sennheiser Electronic Laboratories
in Wennebostel (Germany). The microphone was used for covertly recording
of a conversation, and was used during the Cold War by both Western and Eastern
intelligence agencies. For concealed recording, Sennheiser also developed
the MM-23.
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The MM-61 looks like a fountain pen from which the lower part, the nib,
is missing [3]. Instead of the nib, it has a
miniature coaxial socket
for connection of the audio cable, as shown in the image.
The audio cable
is approx. 95 cm long and has a 2 mm jack plug at
the other end, for connection to a recording device or transmitter.
The pen was normally carried in one of the brest pockets of a coat or
shirt, which was modified in such a way that the cable could be
led through an invisible hole, to the transmitter or recording device
that was carried elsewhere on the body.
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Although the MM-61 was originally intended for use in combination
with dictation machines and the first generation of (large)
hearing aids, it soon became a prime candidate for covert
listening devices and recorders.
When carried casually in the outer pocket of a coat, the microphone
could barely be distinguised from a real fountain pen and would not
raise any suspicion. Because it was overtly carried, the sound quality
was superior compared to that of a concealed microphone [2].
MM-61 was used by intelligence services and police
investigators throughout Europe, but was also one of the favorites
of the repressive East-German intelligence service MfS (Stasi),
where it was often carried by a unofficial employee (IM)
on an infiltration mission or working under cover. [2].
The MM-61 was available in 1964 for a price of DM 46 1
and was in production until ~ 1975.
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List price in 1964: DM 46 (approx. EUR 23).
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Frequency 400 - 4000 Hz Impedance 500Ω Connection Special coaxial socket Cable Supplied, 95 cm, with 2mm jack plug Size 86 mm long, diameter 15 mm Weight 19 grams Shape Fountain pen Material Plastic, with metal clip First sold 1962 Last sold 1975
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© Crypto Museum. Created: Tuesday 15 September 2015. Last changed: Sunday, 04 December 2022 - 14:52 CET.
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