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TT-360
OTT cipher machine (mixer) - wanted item

The TT-360 was an off-line cipher machine for teleprinter networks (telex), developed by Mils Elektronik in Mils (Austria), probably in the 1970s. The machine offers unbreakable encryption, by using the Vernam principle to mix the data from a clear-text tape with the random data from a One-Time Tape (OTT). It was probably the first mixing cipher machine (mixer) developed by Mils.

The image on the right shows the only close-up picture of the TT-360 that we have available at the moment. The unit is 19" wide and has all of its controls at the front panel. It consists of two products: the 304 control unit and one or two 305 optical tape readers. The unit shown on the right has two such 305 optical tape readers.

At the top are two paper tape readers: one at the left rear, used for the clear-text, and one at the front centre, used for the key tape which is fed from the tape reel at the right. A version with just one paper tape reader was also available.
  

The single-reader version was used for online cipher systems and for connection to an external tape reader. For transmission, the setup was complemented by a 306 high-speed tape puncher, which is not shown in the image above. The TT-360 was qualified for all types of transmission, but was mainly used for Radio Teletype (RTTY) over short-wave radio links (AM, FM and SSB).

The TT-360 was developed by Mils Elektronik in the late 1960s or in the early 1970s, and was one of their mainstream products for many years. In 1975, it was demonstrated on the Mils Elektronik stand at the ITU World Telecom Exhibition in Geneva, where the two devices were shown side-by-side. The photograph below shows two identical machines side-by-side.


The rightmost machine is connected to the high-speed 306 tape puncher. The machine at the left is connected to a Siemens T-100 teleprinter. Click here for the full image. In 1979, it was still shown on the Mils stand, where the version with one tape reader was used in combination with a Siemens T-1000 teleprinter. A double setup was used to demonstrate the machines. The TT-360 was succeeded in the mid-1980s by the ME-840 and eventually by the ME-640.

Front view of the TT-360 mixer machine Willi Reichert at the Telecom conference in Geneva in 1975. Photograph by Eberhard Scholz [1]. The Mils Elektronik stand at the Telecom conference in Geneva in 1975. Photograph by Eberhard Scholz [1]. The Mils Elektronik stand at the Telecom conference in Geneva in 1975. Photograph by Eberhard Scholz [1]. The Mils Elektronik stand at the MEDE in Wiesbaden in 1976. Photograph by Eberhard Scholz [1]. The Mils Elektronik stand at the Telecom conference in Geneva in 1979. Photograph by Eberhard Scholz [1].

Similar machines
Although the TT-360 was available from Mils for many years, it was by no means the only mixer on the market. Although it is difficult to establish the first inventor of the mixer, it is assumed that the principle of using the XOR operation (modulo-2 addition) for mixing clear-text and key, was invented by Gilbert Vernam and that Joseph Mauborgne added the application of truely random characters for the key. For this reason, a mixer is often described as a Vernam Cipher.

The first practicle implementation of a mixer was probably the Siemens T-43 that was developed in Germany during WWII. As the machine was introduced relatively late in the war, only a modest number of them were in operation when the war ended. Some of them were confiscated by the Allies and send to the US. The remaining units were destroyed.

Immediately after the war, the Norwegian manufactuer STK, developed the ETCRRM mixer. It was later used on the Washington-Moscow Hotline during the Cold War. The ETCRRM was a valve-based machine that was also used by the Austrian Army and by NATO, until it was replaced by the Lorenz Mixer and the Siemens M-190.

In the late 1950s, the Dutch telecom operator PTT, developed the Ecolex I, their first valve-based mixer, soon followed by the fully transistorized Ecolex II. These machines were built by Philips Usfa in Eindhoven (Netherlands), who later took over development from the PTT. In 1963, Philips introduced the Ecolex IV which would be their last mixer machine before they moved to algorithm-based encryption.

References
  1. Mils Elektronik, TT-360 Punched Tape Transmission Unit
    Sales leaflet. Date unknown, but probably mid 1970s. 1
  1. Document kindly supplied by Mils Electronic.

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