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Opto
Voice
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Dahme 2
Opto-electronic voice transceiver - wanted item

Dahme 2 1 was a transistorised portable opto-electronic device for speech (voice) communication through infrared light (German: Lichtsprechgerät), developed in the early 1960s by the Operativ Technischer Sektor (OTS) of the repressive intelligence service of the former DDR (East-Germany) — Ministerium für Staatssicherheit (MfS), also known as the Stasi. It was combined with a regular 35 mm photo camera that was used as a rangefinder, and was suitable for Short Range Agent Communication (SRAC) – over a distance of 2 km – with a Dahme 1 device at the opposite side.

The device consists of an infrared optical system that is bolted to the bottom of a regular 35 mm camera. It is shown in the image on the right, mounted onto a common photographic tripod. The device is connected to an external amplifier that is not visible in the image. Once the device is aimed at the opposite station, the shutter is opened and the lens is used for the receiver. The infrared transmitter is housed in the lower part.

In 1964, West-German authorities confiscated a Dahme 2 from an East-German Stasi agent, who had used it to contact a station in East-Berlin, located in a house across the Teltow channel.
  
Dahme 2 mounted on a tripod, ready for use.

At the first floor of the house, behind the rightmost window, was a Dahme 1 station. At the time, the East-West border ran through the middle of the Teltow channel. It is believed both devices (Dahme 1 and Dahme 2) were inspired on the American XE-2 device that had been confiscated by the Stasi in 1959, when Western (CIA) agent Gisela Gebhardt was arrested. As far as we know, the only surviving sample of a Dahme 2 is at the Bundeskriminalamt (BKA) — the German Criminal Police in Köln (Germany), which is where some of the photographs below were taken [1].

 More about Dahme 1

  1. The Dahme is a river that flows in the German states of Brandenburg and Berlin. The Stasi commonly used river names for its infra-red (IR) communication devices. As Dahme is pronounced the same as the German word Dame (lady), the name was easily transformed into Dame 2 (lady 2).

Dahme 2 mounted on a tripod, ready for use.
Dahme 2 parts
A demonstration of the Dahme 2
Photograph taken by the German BKA of the house that was used by the Stasi to receive the IR messages.
Dahme 2 confiscated by BKA. Photograph Detlev Vreisleben [1].
Dahme 2 confiscated by BKA. Photograph Detlev Vreisleben [1].
Dahme 2 confiscated by BKA. Photograph Detlev Vreisleben [1].
Dahme 2 confiscated by BKA. Photograph Detlev Vreisleben [1].
Dahme 2 confiscated by BKA. Photograph Detlev Vreisleben [1].
Dahme 2 confiscated by BKA. Photograph Detlev Vreisleben [1].
Dahme 2 confiscated by BKA. Photograph Detlev Vreisleben [1].
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Dahme 2 mounted on a tripod, ready for use.
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Dahme 2 parts
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A demonstration of the Dahme 2
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Photograph taken by the German BKA of the house that was used by the Stasi to receive the IR messages.
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Dahme 2 confiscated by BKA. Photograph Detlev Vreisleben [1].
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Dahme 2 confiscated by BKA. Photograph Detlev Vreisleben [1].
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Dahme 2 confiscated by BKA. Photograph Detlev Vreisleben [1].
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Dahme 2 confiscated by BKA. Photograph Detlev Vreisleben [1].
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Dahme 2 confiscated by BKA. Photograph Detlev Vreisleben [1].
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Dahme 2 confiscated by BKA. Photograph Detlev Vreisleben [1].
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Dahme 2 confiscated by BKA. Photograph Detlev Vreisleben [1].

Specifications
  • Type
    Line-of-sight (LOS) light-based communication device
  • Purpose
    Covert cross-border agent communication
  • User
    MfS (Stasi)
  • Manufacturer
    OTS
  • Frequency
    Infrared
  • Purpose
    Speech, recorded audio
  • Usage
    Indoor (limited outdoor usage)
  • Angle (2ω)
    2° (TX), 0.5° (RX)
  • Bandwidth
    400-2000 Hz ±6dB
  • Range
    2 km (against Dahme 1)
    800 m (against Dahme 2)
  • Microphone
    Sennheiser MM-23
  • Power
    5 to 6V DC
  • Lamp
    100 hours
  • Dimensions
    On-camera unit: 110 x 90 x 38 mm
    Amplifier: 120 x 90 x 17 mm
  • Weight
    On-camera unit: 480 g
    Amplifier: 150 g
Documentation
  1. Dahme 2 Specification
    Original Stasi card. Mfs, Undated. 1 pages.
References
  1. Detlev Vreisleben, Personal correspondence
    November 2021.

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

  3. Detlev Vreisleben, Photograph of Dahme 1 (location)
    Taken at Bundeskriminalamt (BKA), Köln (Germany), 2 November 2004.

  4. Detlev Vreisleben, Photograph of Dahme 2 (device)
    Taken at Bundeskriminalamt (BKA), Köln (Germany), 2 November 2004.
  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].

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© Crypto Museum. Created: Thursday 09 December 2021. Last changed: Monday, 20 December 2021 - 09:56 CET.
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