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Central Intelligence Agency

The Central Intelligence Agency (CIA), is an independent civilian foreign intelligence service of the United States federal government. The agency is tasked with gathering, processing and analysing national security information around the world, mainly through human intelligence (HUMINT) [1].

The CIA was established on 31 December 1948 as the Office of Scientific Intelligence (OSI), by merging the Scientific Branch of the Office of Reports and Estimates, and the Nuclear Energy Group of the Office of Special Operations (OSO). It is also the successor to the Central Intelligence Group (CIG) and, to some extent, to the World War II Office of Strategic Services (OSS).

Although most of the information is gathered overseas, the CIA also collects data do­mes­tically. It is the only US agency which is authorized by US law to carry out overseas covert operations on behalf of the President of the United States (POTUS). Unlike the Federal Bureau of Investigation (FBI), the CIA is not a law enforcement agency and has therefore no legal jurisdiction.

CIA equipment on this website
KL-7 rotor-based cipher machine (USA)
OSS (CIA) aperiodic receiver SSR-201
WWI portable direction finder in suitcase
Project Easy Chair: development of passive bugging devices
Minifon Mi-51, the first wire recorder from Protona
Minifon P 55 covert wire recorder
Minifon Ataché, the first all-transistor tape-based Minifon
Minifon Special, a wire recorder for the secret services.
Type-B probe microphone, based on the RCA BK-6B
Wired Easy Chair - room bugging via analogue telelephone set
Project 'Rocking Chair' (RC) - room bugging via telephone line
Tester for Easy Chair (Mk II)
Resonant Cavity Microphone for 360 and 1100 MHz
Ceramic Shear Tube Contact Microphone
SWM-28 miniature electret condenser microphone used by the CIA
SWM-44/B electret condenser microphone used by the CIA
Miniature microphone elements manufactured by Knowles
290 MHz bug with TP audio masking
350 MHz bug with RP audio masking
1500 MHz covert listening device (bug) with advanced audio masking
Low-power version of the SRT-91
Miniature 350 MHz transmitter (bug) with Dirty Pulse (DP) audio masking
Subcarrier modulated bug from another contractor
Minature 290 MHz transmitter (bug) with SC audio masking
Minature 70 MHz switch-receiver
Subminiature transmitter developed as part of the Super Pulse project
Ilmenau 210 tabletop radio receiver
VEB Sternradio Sonneberg (DDR) - Sternchen
BND short-wave converter
Maico Model R hearing aid, converted for CIA use
Hybrid mains-powered CIA surveillance transmitter ST-2A (bug)
TX-916 Body Transmitter 1W with scrambler
SRR-4 surveillance receiver 50-200 MHz (1958)
SRR-5 surveillance receiver 50-400 MHz (1961)
SRR-8 surveillance receiver 30-1000 MHz (1963)
SRR-23 (ACL SR-209) HF/VHF/UHF/SHF surveillance receiver
SRR-52 listening post receiver
SRR-56 listening post receiver
Improved modular surveillance receiver (vertical model)
Improved modular surveillance receiver (horizontal model)
Modular surveillance receiver for RP and DP masked bugs
CIA surveillance receiver SRR-100
Panasonic RF-015 AM/FM pocket radio
SRR-145 down-converter
SRR-153 surveillance receiver
QRT-153 activation transmitter
Path loss survey system
Path loss survey system (wideband)
Path loss survey system (narrowband)
RX-905 analogue VHF surveillance receiver
RX-1000 digital VHF surveillance receiver
United 225 Intelligence kit (body transmitter and briefcase receiver)
RS-1 (AN/GRC109)
CIA receiver RR/E-11
Automatic CIA agent radio set
Automatic Station 3 (CIA)
QRC-222 suitcase spy radio set (1964) -- also known as RS-8
AN/PRC-64 and Delco 5300
RS-100 integrated spy radio set
TAR-224A spy radio set
RS-49 modular spy radio station
RS-59 modular spy radio station
CDS-501 short-range agent communications
RS-804 satellite message burst transmitter
HRR-18 homing system used by the CIA
HRR-26 homing system used by the CIA
UVK-153 transmitter tester
High-performance mercury batteries developed for the CIA's bugs
Latching radio switch system (remote control)
Microdyne 1100-AR telemetry receiver (also used as intercept and surveillance receiver)
Nagra SN high-end miniature tape recorder
Sub-miniature professional-grade body wearable tape recorder developed for the FBI
Nagra PS-1 playback unit for JBR tape cassettes
Nagra CBR digital Covert Body Recorder
Nagra CCR covert recorder at the size of a credit card (no image available)
 List of known CIA equipment

CIA operations on this website
Operation RUBICON (THESAURUS) - the secret purchase of Crypto AG
Listening devices   bugs
As a foreign intelligence agency, the CIA has always made heavy use of so-called covert listening devices, commonly known as bugs. In the early days of the electronic espionage tradecraft, such listening devices were small microphones that were connected to a listening post through fixed wires, which is why such a bug is also known as a wire (even though today many are wireless).

In the periode following WWII, when effectively the Cold War had begun, wireless radio bugs were introduced, that were built with a mixture of miniature valves (tubes) and early transistors. Good examples of such bugs are the ST-1, ST-2(A) — shown on the right — SRT-3 and SRT-5.

Such a device was known as Surveillance Radio Transmitter or SRT. In most cases they were developed by the CIA, or by a third party on behalf of the CIA. They were neither small nor sophisticated, and could easily be detected by someone who was scanning the radio bands.
ST-2A surveillance transmitter (blue)

In 1952 a mysterious type of listening device was discovered in the study of the US Ambassador in Moscow. The device had apparently been planted there by the Soviets in 1945, and was based on a hitherto unknown technology, which is why the Americans nicknamed it The Thing. In a reaction to its discovery, the CIA initiated a secret research project under the name EASYCHAIR, abbreviated EC, which was actually carried out by the Dutch Radar Laboratory (NRP) in Noordwijk (Netherlands).

This research resulted in the development of a series of bugs that did not need a local power source (such as batteries), but were driven by a very strong radio signal, the so-called activation beam, from a nearby listening post (LP). Such bugs were known as Passive Elements or PE, but they were also identified with the project name Easy Chair or EC. An example is the EC Mark I.

EC devices consisted of a simple dipole antenna with a detector diode, or crystal, and a transistor amplifier that was connected to a microphone. The image on the right shows the EC Mark I.

By the mid-1960s, the technology behind the PE devices was outdated, as both parties (East and West) had meanwhile developed suitable countermeasures against them. Furthermore, both sides had been complaining about their offices and embassies being 'bombarded' by the other party, with strong microwave signals that could potentially cause 'health issues' to their personnel.

From that moment on, a new generation of bugs was developed for the CIA, mainly by external contractors, such as the NRP who had previously made the Easy Chair equipment. These new bugs were identified as SRT followed by 2 or 3 digits, and introduced audio masking techniques that made detection of these devices very difficult.

Examples of such audio masking techniques are subcarrier modulation, hum-injection and noise controlled pulse position modulation. The image on the right shows an SRT-107 and its antenna, which uses rejected pulse (RP) audio masking.

Devices like the SRT-107 were not particularly small by today's standards, but were really state-of-the-art when they were first introduced. They could be fitted in a pre-drilled 1 1/8" hole and were commonly embedded in a building or inside a piece of furniture. It was the CIA's intention to regularly introduce new audio-masking schemes, in order to defeat the Soviet countermeasures.

Development of special surveillance equipment was sometimes carried out by the CIA's Technical Services Staff (TSS) — since February 1960 Technical Services Division (TSD) and since 1974 Office of Technical Service (OTS) — but also by third parties under CIA contract. In the latter case, the project names and designators were always assigned by the CIA. Project numbers consisted of a three letter prefix, followed by 1, 2 or 3 digits. For surveillance radio equipment, the project designator was generally of the form SRS-150, in which SRS means Surveillance Radio System.

In this nomenclature, receivers are commonly identified with the letters SRR (Surveillance Radio Receiver), e.g. SRR-150, and transmitters are known as SRT (Surveillance Radio Transmitter), e.g. SRT-150. Below is a non-exhaustive overview of known receivers and transmitters (bugs) that follow these rules. Devices developed under the Easy Chair (EC) contract between 1954 and 1964, are an exception to this rule. Such devices commonly have the letters 'EC' in their name.

Technical department
  • 1951
    Technical Services Staff
  • 1960
    Technical Services Division
  • 1973
    Office of Technical Service
The online magazine WIRED has made an interesting series of videos on YouTube, in which Joanna Mendez — former CIA Chief of Disguise of the Office of Technical Service (OTS) of the CIA — talks about some of the tactics and CIA gadgets they used during the Cold War. In the video below she speaks about surveillance issues in Moscow, which was one of the most difficult places for the CIA to operate in, as all American personnel was under constant surveillance of the Russian KGB [2].

Former CIA Chief of Disguise Joanna Mendez talks about operations in Moscow [2]

Known CIA equipment
Below is a non-exhaustive overview of equipment that was developed by or on behalf of the CIA. Note that this list is by no means complete. If you know of any devices that are not listed here, please let us know.

Special receivers
Surveillance receivers
Known CIA bugs
Complete surveillance systems
Spy radio sets
Other equipment used by the CIA
Third party equipment

Frequency ranges
The diagram below gives a rough idea of the frequency bands in which the CIA bugs operate. Especially the frequencies between 250 and 400 MHz were very popular for many years. The higher segment around 1500 MHz was used from 1971 onwards.

Frequency bands
Below is a list of frequencies used by the CIA for covert listening devices. Note that the number that is used to identify the band, is an internal CIA designator. These numbers are different from the usual VHF/UHF band designators. The following band numbers are currently known:

Band Frequency Example
0 230-260 MHz SRT-57
1 260-320 MHz SRT-52, SRT-91, SRT-90
2 320-380 MHz Easy Chair, SRT-56, SRT-91, SRT-90, SRT-SP
3 380-470 MHz -
4 1000-1300 MHz -
5 1300-1600 MHz SRT-107, SRT-52-H, SRT-56-H
6 1600-1900 MHz -
Audio masking
Standard continuous-wave (CW) FM or AM radio bugs are easily found with a surveillance receiver that is suitable for the frequency range in which the bug operates. In addition they can be found accidently by someone who is searching the frequency spectrum, or as a result of RF interference with ordinary domestic equipment, such as radio and television sets.

For this reason, the more professional bugs have some kind of audio masking. Most masking techniques involve the use of subcarrier modulation (SC), which is easily defeated by a suitable bug tracer, such as the Scanlock Mark VB. Others involve the introduction of sophisticated novel modulation techniques, such as pulse position modulation. The following schemes are known:

Name 1 Type 2 Description Example
TP 52 PPM + Triple Pulse (TP) SRT-52
RP 56 PPM + Random Pulse (RP) rejection SRT-56
DP 91 PPM + Dirty Pulse SRT-91
DPD 92 Dual channel version of DP SRT-92
SP 91 PPM + Super Pulse (later renamed to DP) SRT-SP
SC ? Subcarrier modulation  
SCH ? SC + hum injection OPEC
SCN 93 SC + noise injection SRT-153

 More about audio masking

  1. The names TP, RP, DP and SP, have been found in internal CIA documentation and might be considered official. The other names (SC, SCH and SCN) are suggested by us.
  2. This column contains the internal scheme number, as used in correspondence between the CIA and developer NRP. It is often (but not always) related to the model number of a known CIA bug.

Below is a timeline that shows when some of the known CIA equipment was developed. Note that the diagram is incomplete and might be altered in the future, as and when new information becomes available. At the center is the time axis that covers the entire Cold War. At the right is the equipment that was developed by the Dutch Radar Laboratory (NRP) under the EASYCHAIR contract during this time. At the left are known listenings devices from other third parties.

CIA abbreviations
CO   Contracting Officer
CIA officer who is responsible for the contact with an external contractor.
COTR   Contract Office Technical Representative
CIA officer who is responsible for the contact with an external contractor on technical matters.
COTS   Commercial-Off-The-Shelf
Generic name for special (restricted) equipment that can be bought readily from from a commercial supplier who also maintains stock. This is in contrast to equipment that is developed aspecially for the organisation.
OTS   Office of Strategic Service
Technical (development) department of the CIA.  more
TCG   The Contracting Group
CIA department reponsible for commissioning (development) work to external contractors.
Equipment nomenclature
  • AS
    Automatic Station (e.g. AS-3)
  • ASR
    Audio Surveillance Receiver
  • AT
    Automatic Transmitter (e.g. AT-3)
  • CK
    Coder/keyer (e.g. CK-8)
  • CO
    Car Overhearing
  • EC
    Easy Chair (codeword)
  • HRK
    Homing Radio Kit
  • HRN
    Homing Radio antenna
  • HRR
    Homing Radio Receiver (e.g. HRR-26)
  • HRS
    Homing Radio System (e.g. HRS-23)
  • HRT
    Homing Radio Transmitter (beacon)
  • LRS
    Latching Radio Switch System (e.g. LRS-1)
  • QRR
    Switch receiver (e.g. QRR-25)
  • QRT
    Activation transmitter or Actuator
  • RC
    Rocking Chair (codeword)
  • RR
    Radio Receiver (e.g. RR-59)
  • RS
    Radio System (or Radio Set) (e.g. RS-6)
  • RT
    Radio Transmitter (e.g. RT-59) 1
  • SAS
    Surveillance Antenna System (e.g. SAS-2)
  • SRK
    Surveillance Radio Keyer (e.g. SRK-145)
  • SRN
    Surveillance Radio antenna (e.g. SRN-58)
  • SRR
    Surveillance Radio Receiver (e.g. SRR-4)
  • SRS
    Surveillance Radio System (e.g. SRS-91)
  • SRT
    Surveillance Radio Transmitter (e.g. SRT-107)
  • SR
    Surveillance Receiver
  • ST
    Surveillance Transmitter (e.g. ST-2A)
  • SWE
    Surveillance Wired Encoder (e.g. SWE-52)
  • SWM
    Surveillance Wired Microphone (e.g. SWM-28)
  • UMY
    (Portable) recorder
  • URR
    Universal Radio Receiver (e.g. URR-1)
  • URS
    Universal Radio System (e.g. URS-1)
  • URT
    Universal Radio Transmitter (e.g. URT-1)
  • UVK
    Universal Validation Kit (e.g. UVK-153)
  • UWB
    Universal Wired Battery (e.g. UWP-301)
  • UWP
    Universal Wired Power (e.g. UWP-52)
  • X
    Used as prefix for prototype equipment (e.g. XSWM-28)
  1. Confusingly, the CIA also used the prefix RT briefly for a series of bugs, such as the RT-3R, before switching over to the SRT prefix.

Secret CIA operations
  1. EASYCHAIR was the name of the secret contract between the CIA and the Dutch Radar laboratory (NRP) for the development of covert listening devices. It was also the name of a covert operation in 1958, in which EASYCHAIR devices were planted in the Russian Embassy in The Hague (Netherlands).

  1. The Hunt for Axis Agent Radios 1
    CIA, Studies in Intelligence, Volume 3, No. 2. Spring 1960.
    Approved for release on 17 December 2004.
  1. Glossary of German terms
    Extracted from Office of Naval Intelligence Report on German and Russian Operations, 1940 to 1945. Approved for release on 7 September 1999.

  2. Standard Communications Equipment List
    CIA, Revised April 1962. Declassified 29 April 2003.
  1. Wikipedia, Central Intelligence Agency
    Retrieved November 2016.

  2. Wired: Former CIA Chief of Disguise Breaks Down Cold War Spy Gadgets
    25 November 2020.
Further information
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© Crypto Museum. Created: Tuesday 22 November 2016. Last changed: Thursday, 14 March 2024 - 10:07 CET.
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