NEMA [Swiss Neue Maschine][click to expand]
NEMA [Swiss Neue Maschine]
[click to expand]
Between 1938 and 1940 Germany supplied the Swiss government with a total of 265 Enigma machines - Commercial Enigma K - which were put to use by the Swiss Army, Air Force and Diplomatic Service. Suspecting, quite correctly, that both the Allies and the Germans were able to read their Enigma-enciphered traffic the Swiss made a number of modifications to these machines which included frequent rewiring of the wheels and, in the case of the Swiss Army, a modification of the wheel turnover. The result was an Enigma that was distinctly different from the standard Commercial machine and which is commonly identified as 'Swiss Enigma K'.
A continuing lack of confidence in the security of their cipher systems led the Swiss to consider designing and building their own cipher machine. Work on the new machine [NEue MAschine] was begun in 1942 but the first two examples were not released for evaluation until 1945 – almost at the war’s end. The Swiss Army and Air Force began to use NEMA in 1947 when over 640 were introduced. NEMA was also known as the Type T-D [Tasten-Drücker-Maschine] and the serial numbers are of the form: T-D XXX.
The design and operating principle of NEMA basically follows that of Enigma. The machine consists of a keyboard with the standard German QWERTZU layout, a wheel -based ‘scrambling’ device and a lampboard - features familiar to those with a basic knowledge of Enigma. Additional features include a character counter on the upper panel, which may be reset by an adjacent lever and a microswitch on the lower left side side of the keyboard panel which disconnects the internal battery when the case is closed. NEMA has no plugboard.
Differences between NEMA and Enigma are apparent at first glance. NEMA is enclosed in an olive-green metal case which measures approximately 36x32x14 cm. and weighs about 10 Kg. Opening the hinged lid reveals NEMA itself which has the general appearance of a portable mechanical typewriter. The keyboard has a total of 31 keys - the normal A-Z alphabet plus three special purpose keys marked WR, ZL and BU and two blank keys. The top row of keys also carries the numerals 1-0. The use of the three special purpose keys is associated with the printer/teleprinter features described below.
The lampboard consists of the 26 letters of the alphabet and two 'blank' windows at the lower right of the lampboard. There is no lamp test socket - a feature common to most Enigmas. The lamp panel is inclined front to back which makes it easier to read by a seated operator. NEMA also has a detachable external lampboard which is stored in the lid of the case along with its cable [about 90 cm in length]. When the external lampboard is in use the normal lampboard continues to function.
The 'scrambler' component of NEMA is very different to that of any of the Enigma variants. It contains ten wheels - marked A-Z. These are actually five pairs of wheels, each pair consisting of a wired component and a control component. NEMA's stepping is much more complex than that of Enigma - it is much more random and there is no 'fast' or 'slow' wheel. Movement of the cross-wired component of each wheel pair is governed by the control component to which it is adjacent. It must be noted here that, with exception of the Eintrittwalze [entry stator] which is a fixture in the machine, and its concentric red, double control wheel, any control component may be matched with any wired component. This pairing is part of the machine setting.
To use the machine for encipherment or decipherment the operator must first remove the nine removable wheels from the machine on their central spindle - the red-coloured control wheel on the right is not normally removed from NEMA during this procedure. The Umkehrwalze [reflector] is included in this action but remains attached to the spindle while the four pairs of wired/control wheels are removed. Each wheel pair is now disassembled - simply by pulling them apart - into its wired component [identified by a letter] and its control component [identified by a number]. The four pairs are then reassembled according to the daily [or other period] machine settings and the wheel pairs are replaced on the spindle in their assigned order. The scrambler is now locked into position, the lid closed and the ten letter message key aligned in NEMA's window. NEMA is now ready for use.
A typical message setting might be:
Wheel setting: UKW 16D 19B 21C 20A 23-2
[23-2 represents the red control wheel which is fixed in the machine].
Message key: UIFNOFWQEJ
Unlike all but a handful of Enigmas, NEMA may be directly connected to either a printing device or a teleprinter via a 34-pin cable. Connection is via a corresponding socket on the machine's right hand side. Power options available to the NEMA operator are an internal 4 volt battery, an external 4 volt battery or accumulator or any AC mains supply having a voltage from 110-250 volts. Input points for these options are found on the right hand side panel. A connecting cable for the AC supply, with a number of adaptors, is carried in the machine's lid.
In 1992 NEMA was declassified by the Swiss Government and a number are now in private hands and museum collections. NEMA is not yet as 'collectible' an item as Enigma and the cost of acquiring one reflects this - being of the order of one tenth or less. Two models are extant - Training and War Reserve. The former has four wheel pairs - A B C D/ 16 19 20 21 - while the latter has additional wired wheels E and F and uses control wheels 12 13 14 15 17 18. The red, double control wheel of the Training model is designated 23-2; that of the War Reserve version is 22-1. When not in use, spare wheels are stored on threaded posts in the lid. Text enciphered by one NEMA variant cannot be deciphered by the other.
There have been numerous instances of a NEMA being wrongly advertised for sale as an Enigma. In some of these cases, gullibility has triumphed over knowledge and common sense and the NEMA has changed hands for an excessively high price. For a list of NEMA and Enigma sales during the past few years click here.
For a more detailed description of the operation of NEMA - particularly the internal details of the wheel movement and wiring - see the recent article [1] by my CSG colleagues Geoff Sullivan and Frode Weierud. To visit the CSG pages click here.
Reference: 1: 'The Swiss NEMA Cipher Machine'; Sullivan, G, and Frode Weierud, Cryptologia XXIII(4): 310-328, October 1999.