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Speech protection unit
SVZ-8/9 is a speech protection unit, or
scrambler, (German: Sprach
Verschleierungs-Zusatz) for the FuG-8
and FuG-9
public services mobile radios,
manufactured around 1985 by Robert Bosch GmbH
in Gerlingen (near Stuttgart, Germany).
It was developed especially for the German Police. 1
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The unit measures 17 x 11 x 5 cm and weights approx. 700 grams.
It was connected externally between an existing
FuG-8
or FuG-9 two-way
radio and the handset. The device is actually a
frequency domain voice scrambler,
rather than a real encryptor, and has 3 modes of operation:
KLAR (clear voice), KRYPTO A and KRYPTO B.
Furthermore it has 8 DIP-switches 2 that are located behind a removable
screw at the front panel. The circuit is built around a
single-chip FX-204
Variable Split Band (VSB) Frequency Inverter, made by the British
company CML [3].
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The FX-204 was developed as a single-chip solution for cordless
telephones and mobile radios, and can be configured as a frequency domain
scrambler, a fixed code scrambler, or a rolling code
scrambler. The A and B settings of the MODE selector at the front panel,
probably refer to two of these operating modes. The same chip was
used in the contemporary
Teltron SP-612 scrambler.
Despite the fact that the FX-204 chip was very sophisticated for its
time, voice scramblers in general, and frequency domain scramblers in
particular, are inherently unsafe. Their 'code' can be broken by a
professional interceptor within seconds. Nevertheless, it provided
reasonable security against occasional or accidental eavesdroppers,
such as the scanner listeners of the 1980s.
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It is believed that they were also used by the German Fire Brigade.
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Only five DIP-switches are actually used.
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The device is housed a a dark green extruded aluminium enclosure, that
consists of a strong rectangular case shell with flat end panels at both
sides One panel holds the front panel controls, whilst the other one is
used to feed in the cables. Each panel is held in place by four screws.
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The circuit is built on a single printed circuit board (PCB) that
measures 10 x 16 cm (Eurocard). After removing both end panels, the
PCB can be removed from the aluminium case shell, as shown in the
image on the right, The actual
FX-204 scrambler chip
is located at the centre.
Neither the PCB, nor the circuit itself, are very sophisticated.
The device is little more than a simple fixed code scrambler
developed from an example given in the datasheet of the FX-204.
Judging from date codes on the components, the device shown
here was made in or after 1986.
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It is hard to believe that a renowned company like Bosch, offered
its customers the SVZ-8/9 as a serious solution for secure voice
communications, as late as 1986, whilst there were plenty of superior
solutions available, such as the
BBC Vericrypt 1100 that, although not
perfect, provided a much better protection by using
time domain scrambling.
In fact, Bosch had been offering the Vericript 1100 as an integrated
solution with its FuG-8b-1
since the early 1980s.
It is possible though, that the SVZ-8/9 was offered as a low-cost
alternative to the expensive
Vericrypt 1100.
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- LS (GND)
- LS (signal)
- Handset Ground
- Handset Microphone
- Handset Ground
- Handset LS
- Handset +12V
- Handset PTT
- Transceiver LS
- Transceiver PTT
- Transceiver Ground
- Transceiver Microphone
- Handset Ground
- Transceiver Ground
- Transceiver Ground
- Transceiver +12V
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The handset is normally connected to the voice protection unit by means of
a standard NATO 7-pin U-77 plug with the following pinout.
Note that this connector is not part of the SVZ-8/9 but of the radio
to which the SVZ-8/9 is connected.
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- n.c.
- +12V
- PTT
- Speaker (ground)
- Speaker
- Microphone (ground)
- Microphone
- Ground
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© Crypto Museum. Created: Wednesday 28 June 2017. Last changed: Monday, 24 October 2022 - 15:10 CET.
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