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← 31217
Stasi
DDR
  
Stock
Vertical stick with RF bug

Stock 1 is a covert listening device (bug) with a built-in 31217-1 transmitter, made in the late 1970s in the former DDR (East-Germany), for use by the state security service of the DDR, the Stasi. The stick has a heavy brass weight at the bottom, with two nails for quick attachment.

The device was probably made for special cases, in which conversations in a room could be over­heard from the room above it, through a tiny hole in the ceeling. In such events, the bug was placed with the bottom of the brass weight over the hole, with the two nails keeping it in place.

The actual microphone is located behind a small 1 mm hole at the bottom centre of the weight. The image on the right shows the complete bug, which consists of two pieces. The thicker part consists of a brass weight with microphone and two nails, and has a 21 cm grey PVC pipe on top.
  
Stick transmitter in action

The thinner part is a black plastic stick that holds the actual 31217 transmitter and the batteries. This was a standard Stasi solution that was available in several variants as shown below. It fits snugly inside the ticker grey outer tube, and connects to the microphone by means of a 3-pin DIN connector at the end. The two individual parts are shown in more detail below. The bug may also have been used in a horizontal position — e.g. when listening through a wall — in which case two supporting pins had to be mounted to the wall first, using the nails as drill markers.

  1. As the official name of this device is currently unknown, we have nicknamed it Stock, which is the German word for Stick.

Microphone (right) with removed 31217 transmitter (left) Stick transmitter in action Heavy weight with microphone Bottom side of the weight/microphone Connector between transmitter and microphone (3-pin DIN) Removable tip at the end of the battery compartment Weight/microphone compared to the size of a hand 31217-1 transmitter embedded in the inner stick
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Microphone (right) with removed 31217 transmitter (left)
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Stick transmitter in action
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Heavy weight with microphone
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Bottom side of the weight/microphone
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Connector between transmitter and microphone (3-pin DIN)
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Removable tip at the end of the battery compartment
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Weight/microphone compared to the size of a hand
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31217-1 transmitter embedded in the inner stick

Features
The diagram below shows the two individual parts of the bug. At the left is the inner stick that has a diameter of 18 mm and is made of black plastic. At the top is a red plastic cap with a bionet fitting, that gives access to the battery compartment, which accepts two 1.5V AA-size penlight batteries. About 2/3 from the top is the actual 31217-1 bug (white). Its antenna is located in the battery compartment, providing an operational range of approx. 150 metres. At the bottom is a 3-pin DIN male plug, by which the inner stick is connected to the microphone of the outer stick.


The outer stick has a diameter of 23 mm and is made of grey PVC. At the bottom is a heavy brass weight with two sharp nails that allow it to be fitted firmly on a wooden floor. At the center of the bottom is a 1 mm hole behind which a miniature dynamic microphone is located. At the top of the brass weight is a 3-pin DIN socket that mates with the DIN plug at the end of the inner stick.

31217-1 transmitter
At the heart of the Stock bug is a medium-range miniature 31217-1 transmitter, developed in the DDR (East-Germany) in the mid-1970s at ITU, for use by the Stasi. The device measures just 32 x 16 x 7 mm and weights less than 25 grams.

It is housed in a silver-plated copper enclosure with a thin white PVC jacket. The device operates in Band V (940-980 MHz).

 More information

  
31217-1 transmitter (bug)

Other sticks
Although the outer tube of the bug featured here, was probably made especially for a specific application, the inner tube was a more or less standard container for the existing bugs at the time, as demonstrated by the image on the right.

The image was taken from an original Stasi document in which the technology was described that was available at the time. [3]. The second one from the right is nearly identical to the inner tube of the bug featured here.

 View the original page

  

Interior
The diagram below shows a cross-section of the Stock. At the left are the batteries. At the right is the brass weight with the microphone. Approximately at the center is the 31217 transmitter with its antenna floating in the battery compartment. To the right of the transmitter are the 3-pin male and female DIN connectors by which the microphone is connected to the transmitter.

Cross-section of the bug

The bottom of the brass weight is somewhat puzzling. It has an outer diameter of 26 mm, with the microphone behind a 1 mm hole at the centre. The two nails are 17.5 mm apart and are held in place by two 2 mm headless screws. The two large holes are equally spaced as the nails, but have a diameter of 4.3 mm and are 14 mm deep. A possible theory is that the nails were used to mark the positition of two supporting pins that were then drilled, hammered or screwed into the floor or the wall, in such a way that the microphone would line up with a pinhole or sound tube.

Bottom of the stick at 2:1 scale

The purpose of the rigs at the bottom of the brass weight, is currently unknown. They are spaced at 2 mm and are similar to a metric screw thread, but it is also possible that they were machined intentionally, for example to improve grip when firmly fitting the stick onto a wooden panel or over the supporting pins. It is also possible that a non-standard brass bolt was used as the base.

Complete device compared to the size of a hand Partly disassembled Stock Removable tip at the end, giving access to the battery compartment. Brass weight with microphone and DIN socket Two white dots to align the inner stick
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Complete device compared to the size of a hand
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Partly disassembled Stock
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Removable tip at the end, giving access to the battery compartment.
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Brass weight with microphone and DIN socket
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Two white dots to align the inner stick

Connections
  1. GND
    red
    +V (GND)
  2. 0V
    blue
    0V
  3. Input
    grey
    Audio
  4. ANT
    brown
    Antenna
References
  1. Detlev Vreisleben, 31217-1, technical description and operating instructions
    Personal correspondence, May - August 2018.

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

  3. MfS, Foto 3, Sendercontainer für Techniken Band V
    GVS-o018, BVfS Pdm-Nr.: 221186. Abt. 26-5. Page 338. 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 kindly supplied by BStU [2] via Detlev Vreisleben [1].

Further information
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© Crypto Museum. Created: Saturday 04 August 2018. Last changed: Tuesday, 25 September 2018 - 11:54 CET.
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