Listening device

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A listening device (also known as a bug ) is a device for the acoustic tracking of all kinds of events. Listening devices can be used in animal research, for example, to follow the sounds they are reproducing without disturbing physical presence. One form used to monitor small children is called a baby monitor . The best-known form of eavesdropping device, however, are devices for eavesdropping on non-publicly spoken words. Such devices do not necessarily have to have a microphone, but can also operate by monitoring telephone lines and radio frequencies.

Bugs made by the MfS for various purposes with magnetic microphones and some with transmitters or amplifiers.

Purely acoustic listening devices

Stethoscope for medical purposes

Purely acoustic listening devices often consist of a funnel that is held to the ear and aimed at the target. They enable remote processes to be followed acoustically. For example, a stethoscope can be used for close-up procedures .

Electroacoustic listening devices

Bending coupler on a fiber optic cable (coupler method)

In electro-acoustic listening devices, a microphone is used to pick up the sound signal. This is transmitted to the receiver either via a cable (also via carrier frequency systems ), a radio link or via an optoelectronic connection. In contrast to wired eavesdropping devices, radio bugs have the disadvantage that they can be tracked down with bug detectors. Wired systems are generally only used if the listening system is a permanent installation and the premises are in the control of the listener.

Wireless wiretapping systems are widely used for spying. VHF and UHF frequencies are mostly used as radio frequencies .

Optical listening systems

Laser microphones are used to monitor rooms. A laser beam is aimed at an object in the room to be monitored (usually a window), which is stimulated to vibrate by the sound waves of the words spoken in the room. The sound information is reconstructed from the beam reflected by the object.

Telephone wiretapping systems

Telephone lines can be tapped wherever they are laid as overhead lines or where there is access to equipment or cable distributors. In this case, the useful signal is usually coupled in inductively, with no click interference. A click occurs, however, when a remote detector switches a test telephone to the same line during a telephone connection.

Wiretapping bugs were being used in telephone systems as early as the early 1930s. The New York Public Prosecutor's Office bugged Lucky Luciano's brothels in order to convict him and prosecute him in 1936.

In the 1950s, the German engineer Horst Schwirkmann discovered eavesdropping devices in the telephone system of the German Embassy in Moscow .

Wiretapping of carrier frequency systems

Signals that are transmitted with the aid of carrier frequency systems (PLC systems) can easily be received in the vicinity of the line with the aid of radio receivers that can receive the frequency ranges used.

Wiretapping of radio frequencies

In principle, radio frequencies can be intercepted with any receiver that can receive the radio frequency to be monitored. If the content of the programs is to be monitored in addition to the pure broadcast activity, the signal must be demodulated and, if necessary, also decoded.

Legal

The operation and possession of purely acoustic listening devices is not prohibited. This also applies to wired systems that are not operated with high frequency. However, the non-publicly spoken word may not be recorded.

With wireless devices, the situation is as follows: CB radios, cell phones and all general sale devices may be bought and used by anyone, but not for monitoring the non-publicly spoken word.

Other devices may only be used by holders of appropriate licenses or their operation is completely prohibited.

See also

Web links

Individual evidence

  1. ↑ Broadband indicator 1071. In: Deutsches Spionagemuseum. Accessed June 24, 2020 (German).
  2. ↑ Time: Russia: Fumigating the Fumigator, September 25, 1964