HF 2.4 Kbps Modem with FEC
TST-4045 was a high speed, high performance short wave (SW)
modulator/demodulator (modem) for the transmission of digital data
via noisy low-quality radio links, with optional
and voice encryption,
introduced in the early 1990s by
TeleSecurity Timmann (TST)
in Tutzing (Germany).
The product is based on a cut-down version of Telefunken's
ETM-1820/M ECHOTEL modem.
It features Forward Error Correction (FEC),
adaptive notch filters, data interleaving, echo cancellation
and signal equalization, using the era's latest developments in Digital Signal Processing (DSP).
It could be upgraded with digital encryption by adding an existing
TST cipher unit internally. For secure speech, the
TST-7698 was added, whilst for data encryption,
the TST-5573 was used. The image on the right
shows an early prototype that is still marked ETM-1820/M on its front panel.
The TST-4045 uses a single-tone transmission protocol that conforms to
NATO's STANAG-4285 standard, and was intended for transmission of high-speed
data, V.24 facsimile, narrow-band secure digital voice, slow-scan TV,
and for transmission of direction finder data and telemetry.
The front panel is nearly identical to that of the
with the exception of the black area at the right, in which an NF-7
audio socket has been added for the device's voice features.
The device was sold to the British Army, for which an
was available [A].
The ETM-1820/M ECHOTEL modem was still available from Telefunken
Racoms 1 in 2018 .
Since 2004, Telefunken Racoms is a wholly owned subsidary of the Israeli company Elbit.
The diagram below shows the front panel of the TST-4045, which is in fact
the same as the front panel of the Telefunken ETM-1820 on which it is based,
with an additional NF-7 socket fitted at the right. This socket is not
present on the Telefunken ETM-1820, and allows a military handset to be
connected to the (optional) TST-7698 voice encryptor
that can be fitted inside the case.
At the rear are sockets for data I/O (X1), a remote control unit (X2)
and an HF or VHF/UHF radio (X3). Depending on the version, a EURO socket
is present for connection to the AC mains, or a custom socket
with an extra fuse for connection to a DC power source
in the range 18 to 32 volt.
Note that the company logo at the left, is that of
Timmann Tele Security (TST),
and not that of
Telefunken Systems Technik
(confusingly also abbreviated to
TST), which was the name that Telefunken in Ulm used for a while,
before it was merged with Deutsche Aerospace (DASA) into Daimler-Benz Aerospace.
In 2004, part of the old Telefunken radio and train technology division was sold
to the Israeli technology firm Elbit and is known today as
Telefunken Racoms .
The TST-4045 is housed in a 1U 19" rackmount enclosure, that in turn could
be fitted inside a desktop enclosure, as shown at the top of this page.
The interior can be accessed by removing the screws from the top panel,
and lifting the panel carefully from the contact strips at its sides.
The interior is roughly divided into three areas. At the left is the
power supply unit (PSU), which in this case is an
AC mains PSU. Other
power options were also available, each with different connectors at
the rear panel. In this case, the holes for the DC power sockets are
covered by a blank panel,
whilst a common 3-pin Euro-socket is available
for connection to the AC mains.
At the center is the actual
DSP-based ECHOTEL modem that was developed
in Ulm (Germany). The circuit board is in fact an
enhanced ISA-bus card that is fitted horizontally.
At the right is Timmann's own optional encryption unit — in this case
a TST-7698 digital speech encryptor —
that could optionally be added to the set. It is shown here with improvised
cabling, indicating that it was indeed a prototype. The connection for the
handset is extended to the NF-7 socket in the black area of the front panel,
whilst the connection to the radio is available at
the DB15 socket marked X3 at the rear.
This socket was also used for connection of the key loader.
ModesSimplex, half-duplex, full-duplex
Speed75, 100, 300, 600, 1200, 2400 and 3200 baud
FEC codingConvolutional coding, soft decision
Modulation2, 4 or 8 PSK convolutional
Tone frequency1800 Hz
MultipathTolerance up to 6 ms
Bandwidth -25dBMax. 3 kHz (0.3—3.3 kHz)
Bandwidth -3dBMax. 2.4 kHz (0.6—3.0 kHz)
Offset/shiftUp to 3.5 Hz/sec tracking
DemodulationCoherent with channel matched filter and equalizer
Mains power93—255V AC, 47—400 Hz (≤25W)
Battery18—32V DC (≤25W)
Dimensions485 x 465 x 44 mm (including grips), 19" rackmount
WeightApprox. 4.5 kg
Temperature-10 to +55°C (operation), -30 to +70°C (storage)
DataEIA RS-232C, DIN 66020, CCITT V.24.V.28
ControlEIA RS-232C, DIN 66020, CCITT V.24.V.28 (internal connector)
Speed75, 150, 300, 600, 1200, 2400, 4800, 9600 baud asynchonous
Audio0dBm, -20dBm to +6dBm (adjustable), 600Ω
4618—32V DC power supply instead of AC PSU
47High security ciphering option for V.24
51Selective call option for DTE 1 software
52Built-in vocoder option for digital voice
53Built-in vocoder option for digital secure voice 2
DTE = Data Terminal Equipment.
Uses the TST-7698.
Kindly supplied by Jim Meyer .
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© Crypto Museum. Created: Wednesday 03 July 2013. Last changed: Tuesday, 20 March 2018 - 14:08 CET.