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Two-way FM/PM VHF radio
KF-802 was an analogue two-way
VHF mobile radio set,
introduced in 1978 by Bosch Telecom
in Gerlingen (Germany). It was
developed for use by German public safety services (BOS),
such as the police and the fire brigade, in compliance with the
German Government's
FuG-8 specicification.
In 1983, optional voice encryption was added.
The radio is commonly known as Bosch FuG-8b
[1].
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The FuG-8 was made by
various manufacturers,
including SEL, Bosch
and AEG Telefunken.
The dimensions of the enclosure and the layout of the
front panel was dictated by the government specification, but internally the
devices were completely different. The image on the right shows the
Bosch FuG-8b-1, which has an extra voice security unit bolted-on at the bottom.
In this particular variant, the Bosch FuG-8 offers two methods for protecting
speech: a rather sophisticated
time domain scrambler
made by BBC,
and a much simpler
frequency inverter.
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Speech scramblers
were very popular during the 1980s with government
organisation such as the police, for protection against occasional
eavesdroppers. They are by no means secure, but offer reasonable protection,
and have the advantage that they work within the existing (analogue)
voice spectrum. This means that they could be added to an existing radio
without altering any circuits.
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The FuG-8b-1 shown here, was introduced around 1983, and had an extra
'blob' at the bottom, that was intended for the (optional) voice
scrambler. It has two extra switches: one to toggle between clear and
secure, and one for selecting the desired voice scrambling method.
By default, the radio uses the internal
Vericrypt 1100 scrambler,
made by the Swiss company Brown Bovery (BBC).
This time domain scrambler,
mixes the order of a finite number of speech fragments
in an ever changing order, controlled by an internal
pseudo-random key generator.
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The key generator is initialised, or seeded, by a
user-configurable cryptographic key, that is loaded into the device
by means of a key loader or filler, that can be connected
to a 5-pin LEMO socket
on the front panel. In normal use, this socket
is covered by a protective rubber cap.
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In order to allow secure voice communication between the various parties,
all mobile radios and base stations have to be loaded with the same
cryptographic key. This means that the keys have to be distributed
prior to the session.
If one of the parties does not have the required key, all parties
have to turn off the scrambler in order to resume the conversation, making it
prone to interception. As a last resort, the FuG-8 shown here, also has
a simple retrofitted
speech inverter
with a fixed mirroring frequency,
that could be selected as an emergency alternative.
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A frequency inverter is the simplest form of a
frequency domain speech scrambler
and offers very little security. in the 1980s, many hobbyist scanner
listeners used a simple frequency inverter to make the conversation audible
again. Nevertheless, it is better than using no protection at all,
if the regular (Verycript 1100) method is not available.
The simple frequency inverter was probably developed by Bosch,
and was introduced in the early 1990s as a mid-life upgrade.
It is known as SVZ and is based
on a single-chip solution, much like the
Bosch SVZ-8/9,
but less sophisticated.
➤ More about the SVZ speech inverter
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The scrambler extension, bolted-on at the bottom of the basic KF-802 (FuG-8)
radio, can be opened by releasing four large bolts in the corners of the
bottom panel, after which the bottom panel can be removed.
The diagram above shows the interior of the speech scrambler extension.
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It consists of a carrier board that holds the extra modules and connections.
At the left is a metal unit, that contains an
FMS identifier, made by
RDN Radiodata GmbH. At the right is space for the
BBC Vericrypt 1100 unit
that is plugged into a 25-way sub-D socket on the carrier board.
It was supplied by Brown Boveri as an OEM unit.
At the right, close to the front end of the case, is a
small PCB
that carries the simple
Bosch SVZ frequency inverter,
that was added as a retrofit solution in the early 1990s. For this addition,
an extra toggle switch was added to the front panel.
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In Germany, the police also used the FuG-8b for sending digital text-based
messages through the air, in order to interrogate the so-called INPOL
database. INPOL contained information about car registrations,
people, criminal records, suspects, terrorism, etc.
Especially for this application,
AEG Telefunken
developed the Telestar
text terminal shown in the image on the right. It had a full-size keyboard
and a built-in thermal printer.
➤ More information
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At the left side of the control unit is a 7-pin U-79U socket,
that accepts a standard NATO 7-pin U-77 plug with the following pinout:
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- n.c.
- PTT
- PTT
- Speaker
- Speaker
- Microphone
- Microphone
- Ground
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- +12.6V
- +12.6V
- +12.6V
- n.c.
- 0V (battery ground)
- 0V (battery ground)
- 0V (battery ground)
- Ruf 1 (1750 Hz)
- Wandler - Ein
- Wandler - Ein
- NFL
- Ground
- NFLR
- Ein
- Ruf 2 (2135 Hz)
- NF- Ein
- n.c.
- A: Empfangsanzeige RSP
- B: +11.6V (UST)
- C: PTT
- D: Speaker (ground)
- E: Speaker (signal)
- F: Microphone (ground)
- H: Microphone (signal)
- J: Ground
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© Crypto Museum. Created: Thursday 29 June 2017. Last changed: Tuesday, 29 September 2020 - 14:29 CET.
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