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31211
Covert RF listening devices · 375 MHz - this page is a stub

31211 is a family of covert listening devices (bugs), developed in the mid to late 1960s, for use by the repressive Ministerium für Staatssicherheit (MfS), commonly known known as Stasi, of the former DDR (East-Germany). The members of the 31211 family all work in UHF Band IV (360-400 MHz) and have various ranges. They were developed in the DDR, Czechoslovakia and Bulgaria [1].

Known models
  • 31211-1
    DDR
    Medium range
  • 31211-2
    DDR
    Medium range
  • 31211-3
    DDR
    Medium range
  • 13111-4
    DDR
    Medium range
  • 31211-5
    DDR
    Long range
  • 31211-6
    DDR
    Short range
  • 31211-613
    Vločka
    Czechoslovakia
    Short range
  • 31211-614
    KOS-8
    Bulgaria
    Short range
31211 bugs on this website
Longe range Stasi RF bug 31211-5
Specifications
At present, only information about the models 1, 2, 5 and 6 is available. The technical specifications of these models are given below. If you have information about any of the other models, or if you have information that is not presented here, please contact us.

31211-1
  • Frequency
    360 - 400 MHz
  • Modulation
    F3 (FM)
  • Voltage
    2.8 V
  • Current
    1.5 mA @ 2.8V
  • Power
    2 or 4 RM12 batteries (switchable)
  • Duration
    ~ 4800 hours (400 days) when using 4 RM12 batteries
  • Antenna
    ¼λ (21 cm)
  • Polarisation
    At will (vertical preferred)
  • Range
    ~ 80 metres
  • Enclosure
    Plastic (containing transmitter, microphone and antenna)
  • Dimensions
    521 x 265 x 23 mm
31211-2
  • Frequency
    360 - 400 MHz
  • Modulation
    F3 (FM)
  • Voltage
    9 V
  • Current
    8.5 mA @ 9V
  • Power
    1 x Pertrix 438
  • Duration
    unknown
  • Antenna
    ¼λ (21 cm)
  • Polarisation
    At will (vertical preferred)
  • Range
    ~ 200 metres
  • Dimensions
    70 x 20 x 16 mm
31211-5
  • Frequency
    360 — 398 MHz (typically 375 MHz)
  • Tuning
    ± 2 MHz (via trimmer)
  • Modulation
    F3 (FM)
  • Deviation
    ≥ 25 kHz @ -70dB (1000 Hz, 600Ω)
  • Audio
    200 Hz — 60 kHz 1
  • Input
    200Ω (e.g. MM-21)
  • Voltage
    7.2 — 10.5V (9V nominal)
  • Current
    ≤ 16 mA @ 9V
  • Output
    12.5 mW @ 9V (50Ω)
  • Range
    400 m
  • Antenna
    ¼λ (21 cm)
  • Temperature
    -20 — +50°C
  • Δf temp
    40 kHz / °C
  • Δf voltage
    0.5 MHz / V
  • Δf env.
    ± 200 kHz
  • Dimensions
    97 x 26 x 15 mm (including lid)
  • Weight
    70 grams
  1. This makes the device suitable for subcarrier audio masking modules.

31211-6
  • Frequency
    360 — 398 MHz
  • Adjustable
    ± 15 — 20 MHz (internal adjustment)
  • Modulation
    F3 (FM)
  • Deviation
    min. 25 kHz @ -70dB audio @ 1000 Hz
  • Voltage
    2 — 3V DC ± 0.5V (2.5V nominal) (6V max.)
  • Current
    1.8mA ± 0.2mA @ 2.5V
  • Battery
    2 x mallory RM12 or ZM12 (or mains PSU)
  • Duration
    1800 hours (75 days)
  • Audio
    300 — 4500 Hz (up to 60 kHz)
  • Input
    200Ω (e.g. MM-21)
  • Antenna
    ¼λ (25 cm)
  • Temperature
    -20 — +50°C
  • Δf voltage
    < 3 MHz / V
  • Δf temp
    ≤ 3 MHz over the entire temperature range
  • Dimensions
    53 x 23 x 13 mm
Documentation
  1. Beschreibung und Bedienungsanleitung für das Gerät 1211-1 / 1211-2
    Description and Operating Instructions for device 1211-1 / 1211-2 (German).
    Date unknown. 3 Pages. 1

  2. 31211-5 Circuit diagram and technical specifications
    Date unknown. 7 Pages. 1

  3. Beschreibung und Bedienungsanleitung für das Gerät 1211-6
    Description and Operating Instructions for device 1211-6 (German).
    Date unknown. 8 Pages. 1

  4. Prüfvorschrift Gerät (und technische Unterlagen) 1211-6P
    Test protocol and technical drawings of device 1211-6P (German).
    Date unknown. 16 Pages. 1
  1. Document obtained from BStU [2] and kindly supplied by Detlev Vreisleben [1].

References
  1. Detlev Vreisleben, 1211 / 31211, technical description and operating instructions
    Personal correspondence, September 2018.

  2. Bundesbeauftragte für die Stasi-Unterlagen (BStU) 1
    Federal Commissioner for the Stasi-Records.

  3. Louis Meulstee, 31211-5 (GDR bugs II)
    Wireless for the Warrier, Volume 4 Supplement, Chapter 124 v1.00.
    Retrieved August 2018.

  4. MfS, Inventurlisten der operativen Technik
    Abteilung 26. Berlin, 10 September 1987. 2
  1. Full name: Bundesbeauftragte für die Unterlagen des Staatssicherheitsdienstes der ehemaligen Deutschen Demokratischen Republik (DDR) — Federal Commissioner for the Records of the State Security Service of the former German Democratic Republic (GDR) — officially abbreviated to BStU.
  2. Document obtained from BStU [2] and kindly supplied by Detlev Vreisleben [1].

Further information
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© Crypto Museum. Created: Friday 12 October 2018. Last changed: Saturday, 13 October 2018 - 10:12 CET.
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