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Štěnice   TI-574A
Czechoslovakian FM radio bug

Štěnice 1 was an FM radio bug, developed around 1968 in Czechoslovakia, by Správa 6 2 for use by the secret intelligence agency (StB) and by Správa 1 (espionage). The device was constructed from the highly modular and customizable TI-574A transmitter and operated at 74-88 MHz, just below the regular FM broadcast band. They were used for domestic as well as foreign espionage.
The transmitter consists of 6 individual modules that were developed for a variety of applications. In combination with the TI-574B receiver, it can be part of a transceiver, a remote control unit, a homing beacon or even a remote controlled bug.

In the configuration shown here, the transmitter measures 150 x 20 x 15 mm, but smaller ones, with less output power, were also conceivable. Although the device is rather large for a bug, such devices were commonly used in permanent installations, for example in a car, behind a wall panel or inside some piece of wooden furniture.
TI-574A transmitter module

The oscillator is crystal-operated, which guarantees a stable and trouble-free transmission. As the modules were also used for hand-held police radios and body wearable covert radios, the VHF-L band (74-88 MHz) was used, which lies just below the regular FM broadcast band. By choosing a frequency at the lower end of this band (close to 74 MHz) the bug can not be received on a domestic radio and will hardly be noticed. The transmitter is powered by a 9-12V DC source.
  1. The name Štěnice might be incorrect as the devices in our collection are unmarked. As Štěnice is the Czech word for Bug we've chosen this as a nickname. The actual device's project number is TI-574A.
  2. Správa 6 refers to Government Department 6: Communication Technology.

TI-574A transmitter module TI-574A transmitter module Bottom view Recovered radio bug Bottom view of recovered bug

Modular design
The diagram below shows the layout of the 500 mW transmitter. The same modules were used in the Přístroj intercept receiver, used for monitoring the French counter-espionage, and in the body-wearable Hvězda 5A radio, that was used by the StB for surveillance and covert operations.

As an example to illustrate how Štěnice might have been used, consider the drawing below. The transmitter could be hidden, together with a large number of batteries, inside a piece of timber with the correct size and colour to fit under an existing table, acting as a fake piece of supporting wood. It is held in place with pieces of sticky tape and could work for weeks or even months.

The bug could be installed in, say, an embassador's office by someone with frequent access to the premises, such as the cleaning lady. On one visit, she could take the exact dimensions and colour of the wood and on the next visit, hidden in the garbage bin, she could bring it into the room and install it under the table. The pin-hole microphone would pick up any conversation in the room without ever being noticed. The above example is a real-life eavesdropping case.
  1. Anonymous, Štěnice - TI-574A transmitter - THANKS!
    Transmitter kindly donated by anonymous former user. July 2015.

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