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Resonant cavity microphone - wanted item

SATYR was a passive covert listening device (bug), developed in the UK in 1953 by Peter Wright at the Marconi Company, for the British intelligence agency MI5. It was inspired on a novel Russian covert listening device known as The Thing, that had been found in 1952 hidden inside the Great Seal of the United States, that hung in the Ambassador's study at the residency in Moscow.

Immediately after the discovery of The Thing, it was flown to Washington (US) and handed over to the FBI, where it was examined at the FBI's Technical Laboratory. On 1 December 1952, the FBI released a technical description of it, along with photographs and detailed drawings [5].

In his book Spycatcher [1], Peter Wright suggests that the Americans had no idea how the device worked – hence the name The Thing – and that they turned to the UK for help, where he (Wright) solved the mystery in 10 weeks time for MI5. It turned out to be a resonant cavity microphone.
To date we have never seen a picture of the actual SATYR device

It is uncertain whether Wright's account is correct however, as it has since become clear from FBI documents that were released in 2014 and 2015, that Wright wasn't the only one trying to solve The Thing's mystery. It is known that the FBI, the SCEL and the CIA had all been running their own research and had all created a series of working replicas, one of which was given to Wright. It is possible that Wright wasn't presented the full picture by MI5 and the American FBI at the time.

In any case, Wright understood the principle behind the device and grasped its potential. At the time (1952) he was still employed as a Navy Scientist, attached to the Marconi Company, where he worked on antisubmarine Radar. After completing his research on the Russian resonant cavity microphone for the Americans, he was asked by MI5 to develop a British variant of it.

After arranging the necessary funding, something that was quite difficult in the days when MI5 officially didn't exist, Wright was assigned a suitable laboratory at the Marconi premises and took off. Approximately 18 months later the new device, that had been codenamed SATYR was ready. It came with a suitcase filled with equipment, and two aerials that were disguised as ordinary British umbrellas. When unfolded, the umbrellas were used as transmitter and receiver dishes [1].

With the device ready for its first demonstration, Wright and his colleague Kemp, went up to the MI5 head­quarters at Leconfield House in Curzon Street, London, and showed it to Deputy Director Roger Hollis. The umbrellas were set up in Hollis' office, whilst SATYR was placed in an MI5 flat just around the corner on South Audley Street.

According to Wright's own account, the device worked perfectly and had a very good audio sensitivity. It was able to pick up any sound in the room, from (test) speech to the turn of the key in the door. Hollis called it Black Magic [1].

After the successful demonstration, SATYR was taken into production and was used in covert operations by the British, Americans, Canadians and Australians. It became one of the best methods for covert eavesdropping during the 1950s, until it was succeeded by new equipment. According to Wright, the Americans 1 ordered twelve sets and cheekily copied the drawings and made twenty more. The whole SATYR operation had great consequences as it established Wright's credentials as a scientist with MI5. In 1954 he would become MI5's first Principal Science Officer.

  1. Here Wright probably refers to the CIA and their project EASYCHAIR. It seems likely however, that the CIA was not aware of Wright's activities at all, as MI5's (and hence Wright's) contact with the Americans on the subject of the Russian resonant cavity microphone, ran via the FBI and not the CIA. It is known that the FBI ordered some British devices for evaluation in 1953 [2]. This is further supported by David Wise in [3], where he writes ...unknown to Karlow and the CIA, British Intelligence had succeeded in replicating the Soviet bug, which MI5, the British internal security service, code-named SATYR.

Help required
No further information is currently available. As far as we know, there are no surviving SATYR devices and there are no images of it in the public domain. Please help us expand this page. If you have any additional information, photographs, drawings or equipment, please contact us.

Technical details
Although it is by no means certain, there are indications that the device had a resonance frequency of 1400 MHz, which whould have been the illumination frequency. It is likely that – like the Russian original – it re-emitted the illumination frequency.

Covert operations
According to Peter Wright, SATYR was successfully used by a number of intelligence services of the English-speaking countries throughout the 1950s, but unfortunately we do not have access to any surviving stories to illustrate this. In his book Spycatcher [1 p.83], Wright gives examples of bugging operations that technically succeeded, but that produced no useful intelligence.

In 1957, Wright went to Montreal (Canada) to assist the RCMP with the installation of two SATYR devices in one of the walls of the future Polish Embassy. Soon after their installation however, the Poles ordered the constructor to remove the wall and replace it by another one.

The RCPM later learned from an informant that the Poles had been tipped off by the Russians.

 More about Peter Wright
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A similar thing happened in Australia two years later, in 1959. The Russians, who had broken off their diplomatic relations with Australia after the Petrov Affair in 1954 [4], were making plans to return. The Australian intelligence service ASIO, wanted to mount a bugging operation against them, and Wright advised them to use a SATYR device, mounted in the wooden frame of one of the windows. One of Wright's assistents went to Australia to help the ASIO installing the device.

As Wright assumed the Russians to be monitoring the building for microwaves right after their return, he instructed the ASIO to leave the device off during the first months of reoccupation. When the device was finally activated, every sound in the room could be picked up, from the shuffling of papers to the scratch of a pen, but not a single word was ever spoken...

Russian countermeasures
Although Wright has always assumed that the Russians had been tipped off by a mole in one of the Western intelligence services, which was probably the case, they had also developed their own technical countermeasures against resonant cavity microphones. After all they were the first to use the technology themselves and had used it against the US Embassy in Moscow for 7 years.

An example of a Russian countermeasures receiver that was developed especially for the detection of resonant cavity microphones, is the OSOBNJAK 8 shown in the image on the right.

The device is housed in an unobtrusive briefcase and can detect strong nearby RF signals between 100 MHz and 12 GHz; the signals that were typically used to activate such microphones.

 More about Osobnjak 8
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  1. Peter Wright, Spycatcher
    ISBN 0-440-29504-1. 1987-1988.

  2. I.W. Conrad to Mr. Harbo, Security survey of the White House
    Internal FBI memorandum. 8 May 1953. 1

  3. David Wise, Molehunt
    ISBN 978-0394585147. 10 March 1992.

  4. Wikipedia, Petrov Affair
    Retrieved January 2016.

  5. J. Edgar Hoover to John W. Ford
    Drawing and Photographs, Russian Resonant Cavity Microphone
    FBI. 1 December 1952. Released to a selected group on 4 December 1952.
    Declassified and approved for release by the FBI on 24 April 2019 persuant to E.O. 13526.
  1. Partly released by the FBI under the Freedom of Information Act (FOIA) on 3 September 2010.

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Crypto Museum. Created: Tuesday 12 January 2016. Last changed: Saturday, 23 July 2022 - 10:08 CET.
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