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Bugs
Stasi
  
33014
Telephone line carrier bug

33014 is a wired carrier-modulated covert listening device (bug) developed around 1981 in the former DDR (East-Germany) for room surveillance by the Ministerium für Staatssicherheit (MfS), also known as the Stasi. The device uses an existing PSTN telephone line for power and transport. In Stasi terminology, the device is known as a TF-B Sender, in which TF means Träger Frequenz (carrier frequency) and B refers to B-Technik (B technology): acoustic room monitoring (bugging).

There are two basic versions: one with a built-in Knowles microphone (33014-10) and one with an external microphone (33014-11). Both types are housed in a metal cylindrical enclosure that is 65 mm long and has a diameter of 12 mm.

The image on the right shows the 33014-10, which has an internal Knowles BT-1759 electret microphone. It can be recognised by the conical plastic tip at the front end. The sound port of the BT-1759 is located behind the small hole at the centre of the tip. The 33014-11 version was used with an external BT-1751 microphone.
  
Wired carrier frequency bug 33014-1

Although the device was suitable for various types of domestic wiring, it was usually connected to a standard analogue telephone line, from which it also drew its power. Any sound picked up in the room, was amplitude-modulated (AM) onto an inaudible carrier and injected back into the telephone line. The audio signal was retrieved elsewhere in the building (or sometimes outside the building) with a special receiver, and relayed to a Stasi monitoring station via a dedicated line.

According to the original Stasi drawings, development of the device was started in 1981, with the first devices being available in 1982. It was in production until at least 1986. In March 1985, a warning was issued for all 33014 devices that had been manufactured until that date. Although the device was designed to allow three units to be connected to a single telephone line – using three different carrier frequencies – it had become clear that this could cause malfunction of the regular telephone service, which could potentially expose the bugs and jeopardize the mission. This was solved by adding an external power supply unit (PSU) in situations with three bugs [C].

Wired carrier frequency bug 33014-1 Knowles microphone built-in at the tip Wiring at the rear end 33014-1 compared to the size of a hand Another view of the 33014-1 33014 partially extracted from its enclosure Bare 33014 PCB compared to the size of a hand Knowles BT1759 microphone
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Wired carrier frequency bug 33014-1
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Knowles microphone built-in at the tip
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Wiring at the rear end
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33014-1 compared to the size of a hand
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Another view of the 33014-1
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33014 partially extracted from its enclosure
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Bare 33014 PCB compared to the size of a hand
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Knowles BT1759 microphone

Setup
The diagram below explains how the 33014 bug was used. At the right is a regular analogue telephone set which is connected to the telephone exchange at the left via a subscriber line. The bug is placed in the room under surveillance and is connected in parallel to the telephone set.


At some point, the subscriber line is tapped and a suitable receiver, or carrier demodulator, is connected to reveal the intercepted sound, which is then monitored or recorded locally, or transferred to a Stasi monitoring station via a leased line. Note that the tapping point can be inside the target building, or even outside the building, with a maximum distance of 5 km.


Versions
There are two basic versions of the 33014: one with a built-in microphone – known as the 33014-10 – and one with an external microphone connected by a short piece of shielded cable – known as the 33014-11. The diagrams below show a cross-section of both versions.

The two basic versions of the 33014 bug


Known variants
  • 33014-101
    With built-in microphone
  • 33014-102
    With built-in microphone
  • 33014-103
    With built-in microphone
  • 33014-111
    With external microphone
  • 33014-112
    With external microphone
  • 33014-113
    With external microphone
Designators
  • 33014-1
    TF-B Sender (basic device)
  • 33014-10
    Version with built-microphone
  • 33014-11
    Version with external microphone
  • 33014-9
    Microphone capsule for 16 mm PCV pipe 1
  • TGL 11689
    PCV pipe 16 mm Ø (type 100) 2
  1. Obtained via Stasi department 26/4.
  2. Obtained via Stasi department 26/2.

Suitable receivers
Carrier frequency
As the device uses an existing telephone line for the transmission of its intelligence, the picked-up audio has to be modulated onto a carrier frequency that is above the human audible range, as otherwise it would interfere with a regular phone call. In the case of the 33014, three such carrier frequencies, or channels, were assigned, allowing up to three bugs to share 1 a single line:

  1. 24 kHz
  2. 40 kHz
    ← the one featured here
  3. 104 kHz
  1. In practice, the number of bugs to be powered from a single telephone line, was limited to two units, as otherwise the line might be malfunctioning and the bug might be exposed. When connecting a third bug on the same line, it had to be powered externally [C].

Circuit diagram
Below is the circuit diagram of the 33014. At the right is the telephone line (a, b) of which the power is rectified in a rectifier bridge, consisting of four BAS20 diodes. At the left is the Knowles electret microphone, which is connected to the input of an USK-14 hybrid modulator circuit. The output of the USK-14 is injected, or superimposed, onto the telephone line via TR1, L1 and C4. Depending on the required carrier frequency, R1, R2 and C4 (purple) were altered accordingly.


The circuit diagram of the USK-14 ceramic hybrid unit – made by KKWH 1 in Hermsdorf (DDR) – is currently unknown. It can not be taken down as it is completely cast in white silicone compound. It is very likely though, that it holds a Voltage Controlled Oscillator (VCO), identical or very similar to the CD4046 (from RCA) [5][6], that was also used in other designs like the 33010 and 33011.

  1. KKWH = Kombinat Keramische Werke Hermsdorf. After the fall of the DDR part of Tridelta, now part of Fraunhofer IKTS (2017) and LUST Hybrid-Technik GmbH [3][4].

Top side of the PCB


Bottom side of the PCB

Interior
The 33014-10 is housed in a metal tube with an outer diameter of 12 mm. At the rear, the pipe is closed with a metal disc through which the (yellow) line wires are fed. At the front is a plastic tip that is shaped in such a way that it forms a sound port for the Knowles BT-1759 microphone.

With the 22014-11, the plastic tip is replaced by a plastic disc through which the microphone lead is fed. The tip and the disc are both held in place by UHU glue. At the rear end, the yellow ground wire is soldered to the enclosure. The inside of the tube is isolated with impregnated paper.

The image on the right shows the front side of the 33014-10, of which the circuit is partially extracted from the metal tube. At the left is the plastic tip behind which the Knowles microphone is located. The top side of the circuit board (PCB) holds the SMDs and conventional components.
  
Dismantling the 33014

At the bottom side of the PCB is a ceramic hybrid circuit that holds the audio pre-amplifier, the Voltage Controlled Oscillator (VCO) and the voltage stabilizer for the VCO. This hybrid circuit was purpose-built at Keramische Werke Hermsdorf (KWH, or KKWH) to the specifications of the Stasi. It has four solder terminals at either side and its parts are covered by a white silicone compound.

Nevertheless, the contours of some of the parts on the hybrid circuit are clearly visible through the silicone. It is certain that a miniature 16-pin chip is located at the centre of the hybrid and that there are several SMD transistors at either side of it. This matches with the CD4046-based circuit of — for example — the 33010 bug [7].

The image on the right gives a sense of the size, compared to a human hand. The image also reveals its construction. At the centre is a thin double sided expoxy printed circuit board (PCB), with the white USK-14 hybrid at the bottom.
  
Bare 33014 PCB compared to the size of a hand

All parts that could not be fitted on the hybrid, are at the top side of the PCB. At the left are three red wires by which the Knowles electret microphone is connected to the PCB. Note that with the 33014-10, a Knowles BT-1759 is used. It is mounted perpendicular to the longitudinal axis of the device, in such a way that its (large) sound port is directly behind the cone-shaped plastic tip.

33014 partially extracted from its enclosure Dismantling the 33014 Removing the PCB from the metal tube Hybrid at the rear of the PCB Top view Bottom view Knowles BT1759 microphone Bare 33014 PCB compared to the size of a hand
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33014 partially extracted from its enclosure
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Dismantling the 33014
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Removing the PCB from the metal tube
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Hybrid at the rear of the PCB
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Top view
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Bottom view
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Knowles BT1759 microphone
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Bare 33014 PCB compared to the size of a hand

Microphones
The diagram below shows the two different electret microphones that were used with the 33014. The one at the left is a Knowles BT-1759 that was used as the internal microphone of the 33014-10, fitted perpendicular behind the plastic tip. The one at the right – a BT01751 – was used with the 33014-11, at the end of a 15 cm long shielded cable. It has a small tube-style sound port.

The two different Knowles microphones

The fact that Knowles microphones were used, is remarkable. Such miniature microphones were developed and manufactured in the USA, and would not have been avaiable during the Cold War, to the countries behind the Iron Curtain. It is possible though, that they were imported under the pretence that they were needed for the manufacture of hearing aids. Ironically, the Knowles sub-miniature microphones were developed during the 1970s and 80s with help and funding from the US Central Intelligence Agency (CIA), who needed them for the production of their own bugs.


Countermeasures
TF-B (carrier) bugs can be discovered with a special bug finder that can handle Long-Wave (LW) frequencies, such as the Scanlock 2000, the Scanlock ECM and the OSCOR 5000.

The Stasi checked its own telecommunication and power lines for carrier bugs, by means of the Capri detector shown in the image on the right. It is suitable for carrier frequencies from 15 to 410 kHz and can recover the audio.

 More information

  
Capri (7042) detector for carrier bugs

Specifications
  • Voltage
    ± 7.5 — ± 60V
  • Current
    < 500 µA
  • Output
    200 mV (into 150Ω)
  • Channels
    3 (24, 40 or 104 kHz)
  • Temperature
    -10 — +45°C
  • Input
    +85dB max.
  • Audio
    300 Hz — 3400 Hz
  • Dimensions
    72 x 12 mm Ø
  • Weight
    14 grams
Documentation
  1. Prüfvorschrift Gerät 33014-1 (test protocol)
    Stasi, 5 December 1983. 2 pages. 1

  2. Kennblatt Gerät 33014-1 (datasheet)
    Stasi, 5 April 1984. 2 pages. 1

  3. Wichtige Einsatzeinschränkungen der Geräte 33014
    Application note, important practical limitations (German).
    Information Linie B 1/85. Stasi, 14 March 1985. 1

  4. Kennblatt Gerät 33014-1 (datasheet)
    Stasi, 23 June 1986. 1 page. 1

  5. Technische Unterlagen Gerät 33014-1 (full technical documentation)
    Stasi, February 1982 — June 1986. 20 pages. 1
  1. Document obtained from BStU [2] and kindly supplied by Detlev Vreisleben [1].

References
  1. Detlev Vreisleben, 33014, technical and historical documentation
    Personal correspondence, July — October 2018.

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

  3. Fraunhofer IKTS, TRIDELTA im Wandel
    Standort-Brochüre Hermsdorf 2017. Prospect (German). Fraunhofer-Institut für Keramische Technologien und Systeme IKTS, November 2017. 70 pages.

  4. Robotron Technik, Keramische Werke Hermsdorf (KWH)
    Retrieved October 2018.

  5. Texas Instruments, CD4046 Datasheet
    2003. Retrieved January 2014.

  6. Application note ICAN-6101, The RCA COS/MOS Phase-Locked-Loop,
    a versatile building block for micro-power digital and analog applications
    October 1972. pp. 614-617.

  7. Louis Meulstee, 33010 (GDR line bugs VI)
    Wireless for the Warrier, Volume 4 Supplement, Chapter 168 v1.00.
    Retrieved October 2018.
  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.

Further documentation
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© Crypto Museum. Created: Sunday 14 October 2018. Last changed: Thursday, 01 November 2018 - 07:45 CET.
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