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Terma ET-10
Military tactical terminal

The ET-10 was a tactical terminal for secure voice communication, developed and built by Terma A/S in Danmark in the early 2000s. It was in fact a digital crypto phone, suitable for connection to Eurocom-based networks with 16 or 32 Kb/s data rate. It was introduced with the German Armed Forces in the mid-2000s and phased out again in 2012. The ET-10 is no longer in production.
The image on the right shows the basic unit of the ET-10. Is is housed in a die-cast aluminium case and resembles a normal telehone set. At the left is the cradle for the handset, which is currently missing. It is connected at the rear.

At the right is a keypad with 20 push-buttons. The bottom row of keys have a built-in LEDs. Above the keypad is a 2-row 16-character LCD display. At the rear are connections for the handset, the (digital) telephone line and the power supply (or battery). Furthermore there is a 25-way D-type connector marked Data/Crypto.
Terma ET-10 Basic Unit

The ET-10 is intended for connection to digital telephone networks based on the military EUROCOM standard, with a data transfer rate of 16Kb/s or 32Kb/s. It is suitable for voice, data, fax and teleprinter communication with a variety of transmission speeds. See the table below for a full list of the available modes. The unit is powered by any polarity power source between 15 and 28V. When first switched on, it tries to auto-sense the speed of the network (16 or 32 Kb/s).
Terma ET-10 Basic Unit Seen from the rear Right side Display Keypad Connections at the rear Handset connector Display after switching on

All connections to the ET-10 are at the rear. The unit is powered by a DC source that is connections to the two black terminals marked 'BATT' by means of banana-type plugs or blank wires. Polarity may be reversed. Two other black terminals are for connection to the line.
The unit is suitable for connection to a 2-wire 16-32 Kb/s digital network. The blank ends of the 2-wire line can be claimed directly onto the terminals. Banana-type plugs can also be used. Optionally, a ground-wire can be connected.

At the bottom-right is the 7-pin socket for connection of the handset. This connector follows the common audio standard currently used by the German Army (Bundeswehr). The handset is currently missing from the ET-10 shown here. Any help on this is appreciated.
Connections at the rear

At the top left is a 25-way D-type socket, marked DATA/CRYPTO. This connector features a full V.24 serial port, allowing the external connection of a fax, a teleprinter (telex) or a computer (data). The connector was probably also used for loading the cryptographic keys (key filler).
Seen from the rear Connections at the rear Rear view Handset connector Display after switching on Close-up of the metal mesh grid over the display

Data modes
The ET-10 can be used in a variety of operation modes, including fax, data and teleprinter (German: Fernschreiber). The default mode is VOICE. The required mode is selected by pressing the MODE button and typing a 2-digit MODE-number. The following modes are recognised:
MODE Type Data rate Class Remark
-- VOICE 16-32Kb/s - Default mode
21 FS 50Bd 2 Fernschreiber (telex), 50 baud, class 2
22 FS 75Bd 2 Fernschreiber (telex), 75 baud, class 2
23 FS 100Bd 2 Fernschreiber (telex), 100 baud, class 2
24 FS 110Bd 2 Fernschreiber (telex), 110 baud, class 2
25 FS 150Bd 2 Fernschreiber (telex), 150 baud, class 2
26 FS 200Bd 2 Fernschreiber (telex), 200 baud, class 2
27 FS 300Bd 2 Fernschreiber (telex), 300 baud, class 2
31 FS 200Bd 2 Fernschreiber (telex), 200 baud, class 2
32 FS 300Bd 2 Fernschreiber (telex), 300 baud, class 2
33 FS 600Bd 2 Fernschreiber (telex), 600 baud, class 2
34 FS 1200Bd 2 Fernschreiber (telex), 1200 baud, class 2
35 FS 2400Bd 2 Fernschreiber (telex), 2400 baud, class 2
36 FS 2400Bd 3 Fernschreiber (telex), 2400 baud, class 3
42 Fax 2.4Kb 4 Fax, 2400 baud, class 4
43 Fax 4.8Kb 3 Fax, 4800 baud, class 3
44 Fax 9.6Kb 4 Fax, 9600 baud, class 4
45 Fax 2.4Kb 3 Fax, 2400 baud, class 3
46 Fax 16Kb 1 Fax, 16 Kb/s, class 1
47 Fax 32Kb 1 Fax, 32 Kb/s, class 1
52 Data 2.4Kb 4 Data, 2400 baud, class 4
53 Data 4.8Kb 4 Data, 4800 baud, class 4
54 Data 9.6Kb 4 Data, 9600 baud, class 4
55 Data 2.4Kb 3 Data, 2400 baud, class 3
56 Data 16Kb 1 Data, 16 Kb/s, class 1
57 Data 32Kb 1 Data, 32 Kb/s, class 1

Key loading
It is currently not know how the cryptographic key was entered into the ET-10. It is possible that this was done manually, via the keyboard, but it is more likely that a purpose-built key loading device was used. Such a key loader (or: filler) was probably connected to the Data/Crypto connector at the rear.
The ET-10 is a very robust terminal with a case that fully complies with TEMPEST regulations. The unit can be opened by removing 8 cross-head bolts from the bottom. Raising the top half of the case, presents a mixed impression of the quality of the unit: both professional and amateuristic.
The top half of the case holds the display and keypad, which are both housed in a TEMPEST-proof enclosure. The display even has a fine metal grid at the front, as to avoid unwanted eminations. This is the professional part.

At the bottom half is an interconnection board that gives a somewhat unorganized impression. Connectors are spread all over the board and the wires are not aligned nicely. Furthermore, the connectors are not sealed to their sockets. This PCB, called the Filter Assembly, is definitely not built to military standards.
Interconnection board

The real beauty of the ET-10 however, is hidden underneath a thick metal plate at the bottom. Removing this panel, reveals the actual digital board of the unit, called the Transmission Circuit. It is a multi-layer PCB with a large number of (custom-built) integrated circuits on one side.
The citcuit is built around a Temic 80C32 micro-controller [2], running at 44MHz, with external Flash-memory, EEPROM (firmware) and battery-backed non-volatile SRAM (8KB) [3]. A series of peripheral chips is present, such as multi-serial controler (Z84C4410), a Counter/Timer Circuit (Z84C3008) and some RS-232 transceivers.

Voice data is digitized with a CML FX609 Continuous Variable Slope Delta Modulator [6] (CVSD). Various custom designed chips (ASICs and CPLS) are used as 'glue-logic', whilst a Harris TA14624 is probably used for crypto.
Harris TA14624B chip

The image above shows the Harris chip amidst the serial controller and the glue logic. At the far right is the 8-bit 80C52 compatible micro-controller. More images of the digitial board below. The digital board has two large 37-pin sockets, roughly at the center of the PCB. These connectors are the only connecton between the board and the 'outside world'. When the PCB is in place, the two sockets protrude the metal cover. The filter board is then mounted on top of them.
ET-10 Interior Interconnection board Four LEDs mounted on the digital board Four plastic light conductors Digital board, top view Harris TA14624B chip Analogue circuitry Custom chip (ASIC) with the Crystal of the Harris chip

Help required
At present we have no further information about the Terma ET-10. If you have more information about this device, for example an instruction manual, or if you have worked with this terminal in the past, we would like to hear from you. As always, your help is much appreciated.
  1. Steen M. Lynenskjold, Supporting the German Armed Forces
    December 2005.

  2. Temic, 80C32 8-bit micro-controller
    14 January 1997. Retrieved November 2012.

  3. Dallas, DS-1225Y Non-volatile SRAM
    February 1998. Retrieved November 2012.

  4. Zilog, Z84C4410 Serial Input/Output Controller
    Date unknown. Retrieved November 2012.

  5. Zilog, Z84C30xx Counter/Timer Circuit
    Date unknown. Retrieved November 2012.

  6. CML, FX609 Continuous Variable Slope Delta Modulation Codec
    D/609/4. 4 July 1994. Retrieved November 2012.

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