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31217-132   Botond
Covert RF listening device

31217-132 — codenamed Botond 1 — is a medium power radio frequency (RF) covert listening device (bug), developed between 1975 and 1980 in Hungary. It operates in the 940 - 980 MHz range (band V) using plain FM. It is concealed as a triangular piece of wood, that can quickly be fitted covertly as an inconspicuous part of an existing piece of furniture, e.g. under a table [1].

The device consists of a machined piece of fibre-strengthened phenol formaldehyde resin, that has milled-out compartments for the batteries, a power switch, the transmitter and its antenna.

The structure is closed with a triangular lid, and is plated with wood veneer that is finished with great precision to make it look like a solid piece of wood. It has two strong embedded nails to allow quick fitting – for example under a table – plus a hole for a more permanent fitting screw. At the bottom is another hole through which the built-in microphone picks up sound in the room.
  
31217-132 (Botond) with cover removed

The device is largely built with components from West-European and American manufacturers. It is typically powered by two 1.5V AAA-size batteries and has a range of 100 to 150 metres. It is activated by removing a pin from the short side. Once activated, it transmits for approx. 5.5 days [A]. Alternatively, it can be powered by a single AAA-size battery (using a dummy to replace the other one), in which case it lasts for approx. 14 days, albeit with a reduced maximum distance.

Botond was developed in the late 1970s, probably for the Hungarian intelligence service BAS, 2 but was also used by the repressive state security service of the former DDR (East Germany)the Stasi – where it was assigned technology number 31217-132 [3]. Although it is part of the Stasi's 31217 family of devices, it is based on a different circuit than DDR-developed devices like the 31217-1, 31217-100 and 31217-111. Other Botond members are 31217-131 and 31217-133.

  1. Botond is an Hungarian male name, that first appeared as the name of a brave solder in an Hungarian legend. It also appears as an Hungarian family name. Literally translated, it means stick or mace.
  2. From 1959 to 1990, BAS (Belügyminisztérium Állambiztonsági Szervek) was the Hungarian State Security Department of the Ministry of Interior, also known as Belügyminisztérium III (Ministry of Internal Affairs III).

Botond compared to the size of a hand Botond Botond bug concealed in wooden triangle Visible side Two spikes for quickly fitting the bug under a table Botond after removing the wooden cover 31217-132 (Botond) with cover removed Botond with the original envelope in which it was released
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Botond compared to the size of a hand
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Botond
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Botond bug concealed in wooden triangle
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Visible side
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Two spikes for quickly fitting the bug under a table
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Botond after removing the wooden cover
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31217-132 (Botond) with cover removed
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Botond with the original envelope in which it was released

Features
Botond measures 111 x 60 x 14 mm and weights 54 grams (without batteries). It has a removable lid that is held in place by three recessed screws at the corners. The device has two strong nails that protrude the lid. With these nails, the device can be attached quickly to a piece of furniture. The diagram below shows the bug with the triangular lid removed and the internal parts visible.


Along the longest side is the actual Botond bug. It is housed in a rectangular silver-plated brass case that measures 50 x 9 x 7 mm, with the antenna sticking out at one end. The micro­phone is located at the bottom of the far end of the bug, and picks up any sound in the room through a hole at the bottom. A microswitch is connected in series with the power line from the batteries to the bug, allowing the device to be turned OFF by inserting a 0.9 mm pin through a hole at the side. In the image above, a paperclip is used to keep the device deactivated until it is needed.

Activating the transmitter by removing the pin Embedded nail for quick-fitting Embedded nail for quick-fitting Pin inserted from the side to deactivate the device Microswitch with blocking pin inserted Empty battery compartment Batteries installed Visible side
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Activating the transmitter by removing the pin
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Embedded nail for quick-fitting
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Embedded nail for quick-fitting
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Pin inserted from the side to deactivate the device
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Microswitch with blocking pin inserted
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Empty battery compartment
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Batteries installed
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Visible side

Suitable receivers
Due to the nature of the design, the frequency of transmitters like Botond has the tendency to drift over time, subject to temperature, battery voltage and any (moving) objects in the vicinity of the device. For this reason, the receiver used for monitoring the signal, must have an Automatic Frequency Correction (AFC) with a wide tracking range. The following receivers were suitable:

Analogue surveillance receiver for the 940 - 980 MHz frequency range
31215
Digital surveillance receiver for the 940 - 980 MHz frequency range
31225
Information about these receivers will be made available in due course




Interior
The interior of the concealment can be accessed by removing three recessed screws at the corners of the wooden lid and taking it off. This reveals a strong fibre-strengthened phenol formaldehyde resin structure with machined compartments, as shown in the diagram above.

The structure accomodates up to two AAA-size batteries, a micro-switch to enable the device, and the actual Botond transmitter. The latter is housed in a silver-plated brass enclosure that measures 50 x 9 x 7 mm, with a curved silver-plated antenna sticking out at one of the ends.

The antenna is curved to make the transmitter more omni-directional. Furthermore, it is pre-shortened to compensate the dielectric effects of the resin body. At the other end of the bug is a Sennheiser MM-301 dynamic microphone, that has its pin-hole sound port at the bottom side.
  
Botond interior. Note the (yellow/red) wire alongside the stripline

Because of the high frequency, the circuit is built onto a ceramic substrate at the bottom of the case. Some tracks are soldered directly to the side of the enclosure (which carries the positive side of the battery voltage) for maximum RF shielding. The RF transistor is roughly placed at the center, with a stripline inductor running to the end of the case. The antenna is soldered directly to the 50Ω impedance point of the stripline. The length of the stripline, and hence the resonance frequency, is determined by the position at which the grey 30 pF parallel capacitor is soldered.

Block diagram
Below is a provisional circuit diagram of the Botond transmitter (bug), created by observing the miniature structures inside the device. As we do not want to take the device apart or otherwise damage it, the value of most components could not be determined. The design of the transmitter is straightforward and is very similar to that of contemporary designs for other frequencies.

At the left is an AF transistor (T1) that is used as a preamplifier for the signal from the built-in Sennheiser MM-301 dynamic microphone. At the right is the oscillator (T2) that resonates at a frequency of approx. 940 MHz. The tuned circuit consists of a short stripline with a 30 pF capacitor to ground, soldered at an arbitrary position to determine the transmission frequency.

Provisional circuit diagram of the 31217-132 (Botond)

The circuit oscillates by the virtue of a short piece of wire from the emitter of T2, that is placed in the vicinity of the stripline. Simple free-running unbuffered oscillators like the one featured here, inherently suffer from the so-called hand effect, which means that the frequency may drift if an object (or a hand) is placed near the bug or its antenna. For the given application, this was not considered a problem, as receivers with a wide AFC tracking range were used for its reception.

Top view of the interior Microswitch Botond transmitter removed from the concealment Botond transmitter seen from its side Close-up of the removed Botond transmitter Botond seen from the top Botond interior. Note the (yellow/red) wire alongside the stripline Close-up of the microphone
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Top view of the interior
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Microswitch
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Botond transmitter removed from the concealment
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Botond transmitter seen from its side
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Close-up of the removed Botond transmitter
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Botond seen from the top
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Botond interior. Note the (yellow/red) wire alongside the stripline
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Close-up of the microphone

Documentation
  1. Information 2/79 Linie B 1
    Battery duration of 31216-1, 31217-1, 31217-131/132/133, NTD, 31218-1.
    1979, 6 pages.
  1. Document obtained from BStU [2] and kindly supplied by Detlev Vreisleben [1].

References
  1. Detlev Vreisleben, 31217-132, technical description and operating instructions
    Personal correspondence, September 2018.

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

  3. Aufgabe B, Inventory list o035-2043/87
    Stasi 1987, page 53. 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. In this document, Botond is erroneously called Botonel.

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© Crypto Museum. Created: Wednesday 19 September 2018. Last changed: Sunday, 23 September 2018 - 06:31 CET.
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