|
|
|
|
|
|
|
RCA CIA Easy Chair
Miniature dynamic microphone
Type-B is a
miniature dynamic microphone,
developed and manufactured around
1958 by RCA
in Camden 1 (New Jersey, US) for the US
Central Intelligence Agency (CIA).
The device is based on the professional TV broadcast microphone BK-6B,
but has a sound port 2 that can be extended with a hollow pipe,
or probe, allowing it to be burried inside a wall
behind plaster or wallpaper.
|
In 1957, RCA introduced the BK-6B microphone as the successor to its
omni-directional BK-6A. It was about half the size of its predecessor
and was intended for the professional TV broadcast market. Nicknamed
PEEWEE it could be carried around the neck with a lanyard in interviews
[A].
According to the brochure [A], it could easily be concealed in a man's hand.
For use as part of a covert listening device (bug), APD 3 provided a new
enclosure that allowed the sound port to be extended with a probe.
The APD-modified BK-6B became known within the CIA as the
Type-B [C].
|
|
|
Extending the sound port of a microphone with a non-metallic hollow tube,
allows the device to be hidden or embedded in a concrete or wooden wall,
and reduces the chance of detection by means of a metal detector, as the
actual microphone is located deep inside the wall. The hollow pipe, or
probe, extends to the surface of the wall, and ends just behind the
plaster or wallpaper, with a tiny pinhole aperture allowing the sound
in the room to reach the microphone's diafragm.
According to a CIA memorandum of 9 July 1957, the first test with the RCA
BK-6B microphones were carried out in the second half of 1957 [4].
Another CIA memorandum, of 6 August 1958 [2], states that
the probe enclosures of
the Type-B were obtained by APD from ASD 4 as
samples of a program done in Frankfurt (Germany).
In March 1959, a Type-B was supplied to the
Dutch Radar Laboratory (NRP) for use with an
Easy Chair Mark III
passive covert listening device (bug), as an alternative to the
Shure MC-30
[3].
Because of the higher fidelity of the Type-B it was found to be more
suitable in certain situations.
|
 |
-
RCA = Radio Corporation of America. It was once one of the most
important developers of domestic and professional audio and video appliences
in the US. Today, RCA is just a licensable brand name.
➤ More
-
The enclosure was developed and made by an unknown party in Frankfurt
(Germany) [1].
-
APD = Applied Physics Division of the.
CIA.
-
ASD = Audio Support Division of the
CIA.
|
At a CIA meeting of 24 July 1958 it was decided that frequency response
curves of the BK-6B (Type-B) with and without the new probe enclosure
would be made [2]. In March 1959, these curves were made available to
the Dutch Radar Laboratory (NRP) [C].
Comparisons were made between pinhole apertures directly on the microphone,
and when using 3", 6", 12" and 18" probes.
The curve for the 3" hollow pipe shown in the photographs above,
is shown here:
➤ See the full report
|
-
Partially released by the CIA on 3 May 2011 under the FOIA.
|
|
|
|
Any links shown in red are currently unavailable.
If you like the information on this website, why not make a donation?
© Crypto Museum. Created: Sunday 02 April 2017. Last changed: Monday, 11 July 2022 - 09:51 CET.
|
|
|
|
|
