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Miniature covert microphones

Shure, also known as Shure Brothers Company, is a manufacturer of audio products, based in Niles (Illinois, USA). The company was founded in 1925 by Sidney Shure as a supplier of radio part kits [1], and has since become a consumer and professional audio manufacturer of micro­phones, wireless microphones, discussion systems, audio mixers and digital signal processing.

Shure company logo. Copyright Shure Corporation.

Apart from complete microphones, Shure also has been supplying bare microphone elements, for use in a wide variety of equipment, including covert listening devices (bugs). One of Shure's major customers in this respect has been the US Central Intelligence Agency (CIA), who used its micro­phones, along those of competitor Knowles, in a range of bugging devices, such as Easy Chair.

Shure microphones on this website
Shure MC-11 microphone element
Shure MC-14 microphone element
Shure MC-30 microphone element
Hybrid mains-powered CIA surveillance transmitter ST-2A (bug)
Easy Chair Mark III - Extended range
Easy Chair Mark V - Multi-channel
The Shure MC-11 was one of the first dynamic microphones to be used for covert listening devices. It is housed in an aluminium enclosure with a diameter of 26 mm. It is 11.5 mm thick and weights 13 grams.

The MC-11 was used in the late 1950s and early 1960s with the first generations of covert listening devices (bugs), such as the ST-2A and the Easy Chair devices.

 MC-11 datasheet

Shure MC-11 microphone

The image on the right shows the MC-14 which is not listed in any Shure brochure, but is believed to be a variant of the MC-11.

They were used in the late 1950s and early 1960s in listening devices like the Easy Chair Mark III and Easy Chair Mark V.

 MC-11 datasheet

Shure MC-14

The MC-30 can bee seen as a smaller variant of the MC-11. It is housed in a rectangular metal enclosure that measures 13.1 x 12.7 x 6.7 mm and weights just 3.5 grams. At the time of its introduction in 1958, it was one of the smallest microphone elements for listening devices.

The microphone has a frequency response of 400 - 4000 Hz and was a direct competitor of the Knowles BA-1501. It was used with bugs like the Easy Chair Mark III and Easy Chair Mark V.

 MC-30 datasheet

Shure MC-30

  • Sensitivity
    -76 dB (1V per microbar)
  • Dimensions
    0.5 x 0.5 x 0.25 inch (12.5 x 12.5 x 6.5 mm)
  • Direction
  • Impedance
    1850 Ω
  • Frequency
    400 - 3500 Hz
  • Shape
  • Element
Known Shure microphones
The following Shure microphones are known to have been used in covert equipment:

  1. Shure, General Catalog No. 58
    1958. Specifications and price of MC30 microphone. Page 17.

  2. Shure, MC11-J and MC30-J Datasheet
    27A136(DJ). 1984. 2 pages.
  1. Wikipedia, Shure
    Retrieved March 2017.

  2. Shure Europe, Shure History
    Retrieved March 2017.
    Page no longer available in 2022

  3. Shure: 007 Things to Know About 1950s and 1960s Spy Microphones
    Chicago, 6 October 2021.

  4. Shure (USA), Shure History
    Retrieved 4 December 2022.
Further information
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Crypto Museum. Created: Friday 31 March 2017. Last changed: Sunday, 04 December 2022 - 15:06 CET.
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