NEMA / T.D.; „New Machine“, manufactured by Zellweger AG, Uster.

The delivery of the last Enigma cipher machines ordered in Germany was more and more delayed, as World War II borke out. So employees of the national cipher office developed a technically improved cipher machine, which was to be manufactured by Zellweger AG, Uster.

Two prototypes were built in 1943 and successfully tested in fall 1944. The mechanically improved machine was built in spring 1945 as „NEMA Model 45“ in a total of 640 machines. These machines came into service in 1947, and they were used by the Swiss army and the Federal Political Department (Swiss ministry of foreign affairs) for more than 20 years. Zellweger NeMa


  • Principle: Cipher machine
  • Modes: Rotor machine, one reflector wheel, four permutation wheels, five stepping wheels

Power Supply

Trockenbatterie 4,5 V


  • 332 x 384 x 148 mm, 10.7 kg


  • Second lamp field
  • Case with reserve wheels Res. Rolls to T.D.


Similar to the ENIGMA, NEMA is a rotor-type ciphering machine with a lamp panel; the machine is more complex in comparison to the ENIGMA and offers better key security.

The NEMA is equipped with one reflector wheel, which is not moved, but only adjusted to the basic position, five stepping wheels and four permutation wheels. In contrast to the ENIGMA, the wheels notches to move the next wheel in irregular intervals, which greatly increases the key security. The stepping and the permutation wheels can be mounted and inserted into the machine in different orders, the key consists of the order of the wheels and a keyword which has to be set with adjusting the wheels in the initial position; this keyword of ten letters and was trnasmitted in the beginning of a telegram and repeated at its end.

When one of the 26 letter keys is pressed down, one of the 26 letters will light up on the lamp panel, depending on the setting of the wheels determined by the initial keyword. Each time a key is pressed, the stepping and permutation wheels are rotated at irregular intervals.

The text to be encrypted is entered on the typewriter keyboard and the ciphertext is copied from the lamp panel and written on a telegram form, which is handed over to the radio operator to be transmitted.

In this kind of mechanical ciphering, one letter is substituted by another, when the same key for the same plaintext letter is pressed several times, it will be replaced by different letters in the ciphertext. The fact that a letter can never be replaced by itself is a weak point of the rotor cipher machines.

Reservewalzen T.D. The case for the reserve wheels for the Nema is rarely found.

Technical Principle

Mechanical cipher machine with one reflector wheel, four permuting wheels and five stepping wheels.

Tube Assembly

No electronic valves are used.


The NEMA was developed by the Swiss army's cipher bureau and manufactured by the Machine Factory Uster, Zellweger AG, which had some experience in precision mechanics, but had never dealt with ciphering technology before.

The entire production took place in a secret project, only a few employees were allowed to wire the wheels in a secret shelter. Since all cases of Swiss Army equipment in the arsenal must carry a label to be reconized from the outside, the NeMa case got the abbreviation T.D., which stands for „Tastendrücker“ (Pushbutton machine).

Component Layout

The machines in the instruction material (for the training of the soldiers) are equipped with other wheels than the KMob machines: these, marked with sticker „To be used only in war mobilization“, have different wheels and two additional exchange wheels usually stored in the cover of the case. Still another set of wheels was used in the machines of the Eidgen. Political Department (Swiss Ministry of Foreig Affairs).

  • Training machines (so-called „school machines“): 220 units
  • War machines (so-called „KMob machines“): 320 units
  • Machines for the embassy communication (so-called „embassy radio machines“): 100 units

The „school machines“, which can be found on the used market, usually have clear signs of wear and have other wheels (other wheel numbers), than the machines for war use. The „KMob machines“, which have never been used in an emergency, are usually used in perfect condition, as they never had to endure the days of heavy use. They are equipped with different wheels, in addition there are two exchange wheels in the lid of the case. (Be careful if you find them missing, there is the possibility that the vendor has taken them out of your machine to complete another machine with missing original wheels.
The „embassy radio machines“, equipped with different wheels again, were almost completely destroyed. Only two machines are said to be still in possession of the Swiss Federation. Since it would have been possible for foreign powers, to use these machines to subsequently decrypt the ciphered messages of the Swiss embassies from after War times, none of these machines was allowed to fall into unauthorized hands.

The cipher machines were used in 1948 - 1979 in the army and in the EPD. The NEMA procedure was declassified in 1992 (ie secrecy abolished) and the machines were sold to the public in May 1994 in the Zeughaus Meiringen for liquidation.

Technical Manuals

Additional Information

en/nema.txt · Zuletzt geändert: 2019/11/24 20:24 von mb