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Crypto Data Telefunken ETM-1810/M → ← ETM-1800
ECHOTEL modem for HF radio
ETM-1810 is a high-end HF radio modem,
developed around 1990 by AEG Telefunken 1
in Ulm (Germany). The device is part of the ECHOTEL family and was used
by the German Army as part of the proprietary MAHRS communication system.
It uses multiple Digital Signal Processors (DSPs).
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The device is house in a 19" 1U rackmountable enclosure with an olive
green front panel. It was developed exclusively for the MAHRS
communication system of the German Army (Bundeswehr),
and was commonly used in combination with the
proprietary ACT-1810 radio processor.
Contrary to its successor, the ETM-1810/M,
it supports only one waveform, which is a variant of
STANAG 4285.
The Forward Error Correction (FEC) was provided by the ACT-1810.
Furthermore it uses a proprietary CONTROL protocol,
as a result of which it cannot be driven from a PC.
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As far as we know, the ETM-1810, was not used in any other communication
system. It is known however, that ECHOTEL modems were used during the
Cold War for a variety of other systems, including the
HF-7000 special forces radio system,
and as part of the base station of the pan-European
stay-behing radio system HARPOON.
At the time of its introduction, the ETM-1810 was available
for a unit price of EUR 47,550.
A more advanced version of the device, with multiple waveforms,
such as STANAG, MILSPEC, FSK, and MSK-LF,
is known as the ETM-1810/M.
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Due to name changes, the ETM-1810 was also sold under the names
Telefunken System Technik (TST), DASA, EADS, Racoms, EADS Racoms,
and Telefunken Racoms.
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Below is the front panel of the ETM-1810. The device is housed in a 19"
1U enclosure and has only two push-buttons at its olive green
front panel:
the ON/OFF switch and a button to start the built-in self-test (BITE).
Furthermore there are four indicator LEDs: two for the result of the self-test
– GO (green) and NOGO (red) – and two for TRANSMIT and RECEIVE respectively.
When the device is switched on, it does a BITE, which can be repeated by
pressing the TEST button.
The rear panel is shown in the image below. It is the same for all versions.
It has three D-sub sockets, marked X1, X2 and X3. The leftmost one (X1)
is a configurable (a)synchronous serial port which carries the decoded
data from the receiver, and the data to the transmitter. The radio itself
is connected to the rightmost connector (X3). The middle connector (X2)
carries a standard serial RS232 port that can be used to control the modem,
completely independently from the data port.
To the right of the D-sub sockets is a small ground connector (X4), which can
be used to properly ground the unit. It can be a banana-type socket or a screw
terminal. At the far right is the mains power receptacle (X5), with built in 2.5A
fuse and mains filter. Note that on some versions X5 is omitted, in which case
it is replaced by a 3-pin XLR male receptacle that accepts 18-32V/DC.
Below is an overview of the versions we've recorded so far, with the firmware
version (when known):
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- ETM-1810
This is a proprietary version of the modem, for use in combination
with an ARCOTEL ACT-1810 radio processor. Approx. 200 units were used
from 1990 onwards by the German Army (Bundeswehr) for its MAHRS radio teleprinter
network. It support a single waveform, which is a variant of
STANAG 4285.
Forwared Error Correction (FEC) was provided by the ACT-1810 radio processor.
This version uses a proprietary CONTROL protocol that is not compatible
with the ETM-1810/M.
The device shown here is of this type.
- ETM-1810/M
This is the extended version of the modem, which supports multiple waveforms.
It has a full front panel with a 2-line LCD display and additional push-buttons.
Furthermore, it uses a different command protocol and can be controlled from
a regular PC.
➤ More
- ETM-1810/M-A
This appears to be an expanded version of the ETM-1810/M above. It is fully
compatible with the ETM-1810/M, but has an extra PCB with two additional
DSPs that provide additional waveforms.
➤ More
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The ETM-1810 must be controlled remotely via the CONTROL port at the rear.
Although we know that this is a regular RS232 serial port, we have no
information about the protocol that is used to drive the device. In any case
it is different from the protocol used with the later ETM-1810/M,
which we've meanwhile been able to unlock. According to former Telefunken
personnel, the ETM-1810 was made especially for the ARCOTEL ACT-1810 computer,
and cannot easily be controlled from a regular PC without deep inside
knowledge. Apparently, some of the features, in particular Forward Error Correction
(FEC), are handled by the ACT-1810 rather than by the ETM-1810.
For now, we assume that the ETM-1810 cannot be controlled easily from a
reguar PC, so it will be difficult to use the device for demonstrations.
Out advise is to look out for the ETM-1810/M instead. It is more versatile,
supports multiple waveforms and we understand some of its protocol.
➤ Check out the ETM-1810/M
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The ETM-1810 is housed in a 19" 1U rackmount enclosure. Its interior can be
accessed from the top, by removing 9 recessed screws from the top panel and
lifting the top panel upwards. Note that the top panel is tightly fit at
the sides by two rows of RF-shielding contact strips.
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The image below shows the interior of the ETM-1810/2, which is the eldest
version in our collection. According to the date codes on the components, it
was built around 1990. Inside the device is a low-profile PSU, which
can be an AC/DC or DC/DC converter. Furthermore, there are three
printed circuit boards (PCBs): (1) A large board at the bottom, (2) a
smaller board mounted in a metal cradle above it, and (3) the front panel PCB
that carries the controls, indicators and display.
The lower PCB (1) (DA-1810) is the main board to
which all other parts are connected. It holds a Texas Instruments
TMS320C25 Digital Signal Processor (DSP), which is also used as the main
controller. It also holds a ZILOG Z0853006 Serial Communication Controller (SCC),
which handles the data ports at the rear. There are also
two audio transformers (TR1 and TR2) and a relay (RS1).
The upper PCM (2) (DS-1810) is the
digital signal processor. It is mounted in a metal cradle, fitted above the lower
PCB, and is connected to the lower PCB via a wide connector.
There are two Motorola XSP560012 DSPs with firmware and RAM.
The board has space for an additional DSP, but that part of the PCB is
not populated.
The smallest board is the front panel PCB (3), which is hidden behind
the front panel. It is connected to the lower PCB via a 10-wire
ribbon cable.
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The DATA port is a bidirectional modem port. It allows data to and from a
computer to be passed to and from the radio. It is a standard asynchronous
RS232 (V.24) serial port, for which a regular DB25/M to DE9/F cable can
be used. Note that the baudrate and the data format are different for each
waveform. For example: the default setting for FSK is 50 baud 5N3
(3 means 1.5 stop-bit).
The default setting for STANAG is 38400 baud 8N1.
Switching from RX to TX can be done by raising the RTS/DTS lines.
This will activate the TX indicator at the front panel.
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| X1 | DE9 | Name | Description |
| 2 | 3 | TXD | Transmitted data |
| 3 | 2 | RXD | Received data |
| 4 | 7 | RTS | Request To Send |
| 5 | 8 | CTS | Clear To Send |
| 6 | 6 | DSR | Data Set Ready |
| 7 | 5 | GND | Ground |
| 8 | 1 | DCD | Data Carrier Detect |
| 20 | 4 | DTR | Data Terminal Ready |
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USB dongles —
An RS232-to-USB dongle may be used for connection to a modern PC,
but it should be noted that not all dongles support all baudrates. Furthermore,
the dongle may not support all control lines (DCD, CTS, DTR) and handshake options.
For proper operation of the ETM-1810, all baudrates, control lines and handshake
options are needed. Cheap dongles should be avoided.
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The modem can be controlled externally via the CONTROL port.
According to former Telefunken personnel, it can only be controlled
from a ACT-1810 radio processor (German: Funkprozessor) [4].
The CONTROL port is a regular RS232 (V.24) asynchronous serial port, for which a
standard DB25/M-to-DE9/F cable can be used.
The speed for this port is fixed at 4800 baud 8N1.
The CONTROL protocol is currently unknown.
Below is the pinout of the DB25 socket (X2) when looking into it. The
first column of the table below holds the pin number of the DB25 connector.
The second column shows the corresponding pin on the DE9 connector
at the PC-side.
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| X2 | DE9 | Name | Description |
| 2 | 3 | TXD | Transmitted data |
| 3 | 2 | RXD | Received data |
| 4 | 7 | RTS | Request To Send |
| 5 | 8 | CTS | Clear To Send |
| 6 | 6 | DSR | Data Set Ready |
| 7 | 5 | GND | Ground |
| 8 | 1 | DCD | Data Carrier Detect |
| 20 | 4 | DTR | Data Terminal Ready |
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The DA-15 socket marked RADIO (X3) is for connection of the ETM-1810 to
a receiver or a transceiver. Below is the pinout when looking into the socket,
as far as it is currently known.
X3 is the connector at the rear. X152 is the internal connector with the
ribbon cable.
Note that this information is obtained from
reverse engineering the device [4]. Consequently, there may be mistakes or
missions. If you find any errors, please let us know.
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| X3 | X152 | Name | Description |
| 1 | 1 | IN | Audio from receiver (600Ω) |
| 2 | 3 | IN | Audio from receiver (600Ω) |
| 3 | 5 | GND | Ground |
| 4 | 7 | ? | 4.25V (PTT?) |
| 5 | 9 | ? | ? |
| 6 | 11 | ? | ? |
| 7 | 13 | ? | ? |
| 8 | 15 | ? | ? |
| 9 | 2 | GND | Ground |
| 10 | 4 | OUT | Audio to transmitter (600Ω) |
| 11 | 6 | OUT | Audio to transmitter (600Ω) |
| 12 | 8 | ? | ? |
| 13 | 10 | ? | ? |
| 14 | 12 | ? | ? |
| 15 | 14 | ? | ? |
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Cable from E-1800 to ETM-1810
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| ? | (X3) | |
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| E-1800 | ETM-1810 | Name | Description |
| 1 | 1 | RX | Audio in (600Ω) |
| 2 | 3 | GND | Ground (shield) |
| 3 | 2 | RX | Audio in (600Ω) |
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Cable from RX-1001 to ETM-1810
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When connecting the ETM-1810 to a Hagenuk RX-1001 receiver, use the following wiring:
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| ? | (X3) | |
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| RX-1001 | ETM-1810 | Name | Description |
| 1 | 1 | RX | Audio in (600Ω) |
| 2 | 2 | RX | Audio in (600Ω) |
| 6 | 3 | GND | Ground (shield) |
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Devices with a DC/DC type power supply unit (PSU), can be powered by
a 18 to 32V DC source, such as a truck battery (24V), that should be
connected to the 3-pin male XLR receptacle
at the rear (X5).
Below is the pinout when looking into the receptacle. 1
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| 1. | (+) | red | +18 to 32V DC 2 |
| 2. | (-) | blue | 0V DC |
| 3. | GND | yellow/green | Ground |
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Note that this pinout does not follow any existing convention!
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The BM-3000 DC/DC converter can actually take 14-70V DC.
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Device HF modem with FEC and ARQ Purpose Reliable data communication via HF radio Model ETM-1810 Name ECHOTEL Manufacturer AEG Telefunken (TST) Year 1985 NSN 5895-12-349-4465 Predecessor ETM-1800 Successor ETM-1810 Used with MAHRS, ACT-1810 User Bundeswehr (German Army) Waveform STANAG 4285 (variant) Speed 4800 baud (see below) Power 230V/AC or 18-32V/DC (typically: 24V) 1 Dimensions 485 × 465 × 44 mm Weight ? Price EUR 47,550
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The following equipment is known to be associated with ECHOTEL:
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- Telefunken Racoms, ECHOTEL ETM 1810/M
Website, 2009. Retrieved May 2013. 1
- Roland Prösch, Technical Handbook for Radio Monitoring
2003. Retrieved February 2018.
- Wikipedia, STANAG 5066
Retrieved March 2018.
- Anonymous former Telefunken employee
Personal communication, March 2018.
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Page no longer available (not even via WayBack Machine).
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© Crypto Museum. Created: Tuesday 20 March 2018. Last changed: Thursday, 12 June 2025 - 09:27 CET.
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