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Working instructions

for the

"Nema" encryption machine

The importance of encryption and decryption requires that all experiments and discoveries which are made in this field be treated with absolute secrecy.


This manual is secret



The Nema or T-D (Tastendrücker) machine encrypts and decrypts documents according to an extremely secure mechanical system. The internal key of the machine is determined electrically by 5 contact segments, and mechanically by 5 crowns of propulsion. It is possible to modify the code easily by rearranging these discs and crowns. For the external adjustment of the key, the discs and crowns have the letters A to Z around their circumference. The external key is formed by the alignment of the letters composing the selected code word.

After having adjusted the machine according to the agreed upon code word, one can transmit the message by pressing the keys which correspond to the text of the message. With each keystroke, the encrypted letter is illuminated on the lamp panel.

To decipher the text, one types the letter to decipher, which in turn illuminates the letter corresponding to the text of the message.

Each key must be in pressed all the way to the bottom before letting it return to its home position and going to the following letter. Use the index fingers to type. Do not touch-type using 10 fingers.

Each keystroke increments a counter which can be brought back to zero. The keyboard includes the 26 letters of the alphabet, with additional keys for an electric typewriter, a teleprinter, a "Hell" text writer, or a "Creed" puncher.

The T-D machine is powered by an electrical outlet, by a dry battery, or by a 4 to 6 volt external power source. For power by an electical outlet, the transformer placed inside the machine lowers the power to 4.5 V.

To make encrypting and decrypting faster, one can connect a second lamp panel to the machine. A second person can thus note the letters appearing on the lamp panel.



A. General.

  1. Size: 332X384X148 mm between the ends. 
    Weight: 10.7 kg with the accessories.

  2. Construction. 
    The machine is assembled in a portable box out of armoured wood [*]; it is fixed on the bottom by means of 3 permanent screws. The external lamp panel, and spare parts, are in the lid. The 2 side hinges can maintain this lid in two different positions: either completely brought back behind, or semi-open. This second position protects the keyboard and the lamp pane against strong light or rain.

    Inside the lid are two grips which are used to hold a sheet of text for easy viewing by the user.

  3. Closing. 
    The box is provided with a safety lock supplemented by 2 metal latches.

B. Encrypting Machine (illustration 1).

Superficially, the machine resembles a typewriter and includes the following principal parts:

  1. the keyboard,

  2. the lamp panel,

  3. character-counter,

  4. the power source input,

  5. switches,

  6. the drum release,

  7. the drum,

  8. the propulsion mechanism.


  1. Keyboard (illustration 1, 2). 
    The arrangement of the 3 row keyboard corresponds to that of an ordinary typewriter. The top row contains both number and letters. A direct connection to a teleprinter, a "HelI" printer, or a "Creed" puncher is made by means of a small, self-powered box with the following keys:

    press WR for the return of the carriage of the typewriter; 
    press ZL for the change of line; 
    press BU for the starting of the teleprinter; 
    press the space bar for spaces.

    These keys are only control signals for the supplementary devices; they do not affect the encryption mechanism.

    The two key stationary keys in the bottom row serve only to complete the keyboard.

    Pressing a key rotates a variable number of discs in the drum via a cam device according to a code. By doing this, these discs create a "lamp-press" circuit according to the code which is closed and opened by the movement of the key. The work and rest contacts are assembled on two supports, of which one, that of the contacts at rest, is on top and the other below the keyboard.

  2. Lamp Panel (illustration 1, 2). 
    The arrangement of letters on the lamp panel is the same as that of the keyboard. Only the illuminated letters count.

  3. Character-Counter (illustration 1, 2). 
    Each letter pressed is recorded by the character-counter, except the first after setting the rotors with the code word (see chapter III B e, p. 22). The character-counter can be brought back to zero by the lever placed to the right. The recording of each keystroke helps keep track of the text to be transmitted. If the number displayed on the character-counter is not fully visible, if it is between numbers, it is because the key was not fully depressed. In this case, it is necessary to restart encrypting or decrypting from the very beginning to avoid transmission errors.

  4. Power source (illustration 1, 2). 
    For power, the Nema machine needs alternating or direct current, or from 4 to 6 V, and approximately 0.4 Amps. 
    Here are possible sources of power: 

    1. A dry battery of 4.5 V placed in the compartment made for this purpose, that is to say a LSA 1004 battery or a battery from an ordinary flashlight.

    2. Connecting the Nema machine to an electrical outlet. This connection must be preceded by the adjustment of the power selector by means of the white screw. The transformer placed in the machine, protected against short-circuits, delivers the necessary power.

    3. A connection to direct or alternating current from 4 to 6 V. This connection is made either at the two 4V leads, or at the input panel on the side.


  5. Switches (illustration 1, 2). 
    There are two of them: 

    1. The power selector switch with the positions:

      "Batt." to use a dry battery. 
      "Trafo" to connect to an electrical outlet via the transformer. 
      "Accu" for other available power sources from 4 to 6 V.

    2. The switch in the lid. 
      The circuit is disconnected when the lid of the box is closed. 

  6. Drum release mechanism (illustration 1, 2, 3). 
    The drum release is operated by the red lever, making it possible to insert, remove and service the rotors. The three positions of this lever provide these functions:

    1. advanced to the "marche" position ("run"). 
      This position activates the keyboard for work.

    2. raised to the middle position "ajuster et répéter" ("adjust and repeat"). 
      In this position, the rotor lid is open. The rotors can be turned in either direction to set the group of the 10 letters of the code word. 
      If the wrong key was pressed, one can make the necessary correction while bringing the red lever back carefully and without shaking to the "ajuster et répéter" position and then setting it to the "marche" position. 
      The next correctly entered keystroke which follows the correction, is not recorded.

    3. completely brought back behind, with the lid of the machine opened. 
      In so far as the release mechanism is not blocked by a lead, one can remove the entire drum, except for the red crown of propulsion.


  7. Drum (illustration 2, 4). 
    It includes:

    A spindle with a fixed disc and 4 double-discs which slide onto it. Each double-disc is comprised of a contact segment and a crown of propulsion which can be separated simply by a suitable side movement. The red crown of propulsion which remains in the machine can be also extracted by an axial movement towards the left.

    The contact discs have one side with contacts in the shape of a "V", and the other with spring-loaded radial contacts. The side of the latter contains a letter of the alphabet (for example A B C, etc).

    It is forbidden to unscrew and open the contact segments.

    The crowns of propulsion are placed on the range of the contact segments (contacts in the shape of a V). Surrounding the side which has the "V" shaped contacts (on the left-hand side) is the distinctive figure of the toothed ring (e.g. 13, 14, etc).

    The toothed ring assembled against the crown by 3 screws is removed by withdrawing those.

    The internal code of the Nema machine is created by the grouping of the discs, and the choice of the interchangeable toothed rings.

  8. Propulsion mechanism (illustration 3). 
    The drum propulsion mechanism includes 11 pawls [*] assembled on a beam. This beam is actuated by the alphabetical keys operating a common spindle. The pawls and by their intermediary the stop of the discs are controlled by the toothed rings of the crowns of propulsion.

C. The extra lamp panel (illustration 1, 5).

This panel connects to a multipolar catch by the connection cord. The same applies to the small box for connecting to an electric typewriter, a teleprinter, a "Hell" script writer, or a "Creed" puncher, which is not part of the "Nema".

D. Accessories and spare parts (illustration 1, 5).

In the lid of the box are placed the following parts:

  1 external lamp panel connect by a fabric cable 
  1 multipolar cord for the connection to this panel. 
  1 cord for connecting to an electrical outlet (4 m length, with 3 wires). 
  1 light socket power adaptor. 
16 extra lamp-panel bulbs (3.5 V; 0.2 Amp.). 
  2 protective lids (which one can fill) each one containing: 

1 spare double-disc

  1 protective lid (which one can fill) containing: 

8 space toothed rings 
1 spring tightener. 




A. Connection to the power source.

  1. Inserting a day battery.

    1. Put the red lever into the "ajuster et répéter" position and unscrew the lid of the machine maintained by 2 capscrews ringed in red.

    2. Open the lid of the battery compartment by moving the bolt in the direction of the arrow.

    3. Remove the protective cover of the new battery.

    4. Insert the battery so that the contact plates of the LSA 1004 battery press against the contact springs located in the battery compartment. If one uses a flashlight battery, fold the contact plates first of all as shown it the following sketch: 
      Then insert the battery straight into the compartment as indicated above.

    5. Close the lid of the compartment.

    6. Close the lid of the machine and tighten the 2 fastening screws.

    7. Put the red lever at the position "marche" .

    8. Set the power switch to the "Batt." position.


  2. Power by electrical outlet. 
    (When the votage is not known, it is enough to read it from the light bulb.)

    1. Configure the power switch to available current by means of the white capscrew on the right side. Loosen this screw, and set it to the voltage corresponding to that of the outlet and tighten it again.

    2. Connect the machine using the power cord to the electrical outlet nearest to a nearby light by using the light socket power adaptor.

    3. Set the power switch to the "Trato" position.


  3. Power by 4 to 6 V source (for example accumulator).

    1. Connect the 4Vpower source to the 2 leads, or at the plugs on the side.

    2. Set the power switch to the "Accu" position.

B. Using the machine.

Encryption and decryption by changing only the external key code.

In this case, the various discs of the drum and their order of continuation which determines the internal key were already fixed and possibly leaded. If a leading were made, the drum cannot be removed any more. The discs cannot be actuated for the fitting of the key of the external code, C-with-D. for the formation of the corresponding word that when the red lever is in the "ajuster et répéter" position.

  1. Place the red lever at the "ajuster et répéter" position.

  2. Form the code word along the edge of the opening by arranging the letters of each disc. A stopping device prevents these discs from moving themselves.

  3. Place the red lever at the "marche" (run) position.

  4. Bring the character-counter to zero.

  5. After each new adjustment of the code word, press "vacuum" on any alphabetical key. The first of the letters pressed, after having moved the red lever position from "ajuster et répéter" to "marche", is not recorded by the character-counter and does not actuate the drum. This is why one speaks about "typing with vacuum". This step should not be forgotten and it does not count for the forwarding of text. It is meant to be be part of the operation of the machine. If it functioning correctly, only one illuminated letter will appear on the lamp panel.

  6. Set the code word once again and set character-counter to zero. (If it is not the case, repeat the steps A throught F.)

  7. To close the lid of the drum.

  8. Encrypting or decrypting. 
    Press all the way on each alphabetical key corresponding to the text and to let it return freely to its home position before pressing the following one. One should only use the index finger. The pressure on the keys must be rather strong, without exaggeration. If you do not press on a key all the way, the drum will not engage correctly. That distorts the text and this cannot be corrected. While pressing on an alphabetical key, one will see the corresponding letter of the text which one encrypts or decrypts, lit up on the lamp panel .

  9. Repetition. 
    If, by error, one did not press on the right key and that one realizes this before having pressed on the following letter, one can correct the fault without distorting the text which remains to be transmitted:

    Put the red lever into the "ajuster et répéter" position without letting it jump, then move it to the"marche" position. Then press on the correct key and to read the letter which appears on the lamp panel.

This repetition is not recorded by the character-counter. The discs of the drum do not move either. In case of doubt also one can repeat, for example, when one believes to have mis-read. One can however repeat only one letter, therefore never several letters in the file.

(There is still another possibility of simpler repetition, but it is applicable only when it is about a typing error, and only if, at the time when one realizes it, the key is still depressed. In this case one presses on the correct letter before releasing the other. The letter which appears on the lamp panel is then is correct.)

C. Modification of the internal key.

The modification of this key and the removal of the lead of the leaded machines should be done only on special order of the head of the transmissions.

  1. To lead the red lever to the position "ajuster et répéter" .

  2. To open the lid of the machine after having loosened the 2 fastening screws.

  3. To bring back until the back the red lever, which makes it possible to release the drum.

  4. To seize with 2 hands the drum without the red crown (which remains in the machine), or is separately removed to press it a little in the axial direction and to leave it the machine.

    Do not force!

  5. To remove the 4 discs double tree, the disc of end remaining on the axis.

  6. To take the 4 discs double one after the other and to separate each disc de' contact (marked by an alphabetical letter) from the crown from propulsion (marked by a figure).

  7. To refom the drum according to the new internal key. To couple say it ques contact with the crowns of propulsion. To slip the discs double thus formed, one after the other on the tree in the order close crit, all the contacts in the shape of V being directed towards the disc of end (p. e.g. 15 D-11 A-14 B-12 F-10/1). The last group of figures indicates the formation of the red crown of propulsion.

  8. To seize the drum with 2 hands, by pressing the discs slightly one against the other, and to introduce it side right-hand side into the stage of the roller distributor and the left side in the mechanism of the red lever.

  9. To lead the red lever to the position "ajuster et répéter" what puts the drum in its position of fitting. [Note about missing "j"]

  10. If the machine must be leaded, to assemble the bent part existing for this purpose until its higher stop, then to introduce the wire into the two holes thus put one opposite the other and to carry out leading.

  11. To close the lid of the machine by tightening the two fastening screws.

  12. To form the external key by aligning the group of the letters which forms the word of code along the former edge of the opening, then to continue to prepare the machine according to instructions' of the chapters III B B with H, pages 21-22.

To modify the internal key, one can change the rings toothed on the crowns of propulsion. It is enough for that to unscrew these rings maintained by 3 screws. To take guard, this concealing, that the chittre engraved on the ring is exactly with the same height as the letter U of the crown. While holding the red crown of propulsion in hands with the letters in the good direction, the toothed ring on the left side must be assembled with the distinctive figure at the level of the letter U and the toothed ring on the right side with the distinctive figure at the level of the letter L the right side must be provided exclusively with numbered toothed rings from 1 to 9 and the right side with those numbered from 10.



When the machine is not used, close the lid of the box. Remove dust carefully at least once per week. The contact springs must be always clean.

Do not to leave in the machine an exhausted battery, because the materials which it contains can cause corrosion to important parts of the machine.

After approximately 200 hours of service or at least once per year, oil the moving parts with a liquid oil which does not solidify.

From time to time it is also necessary to clean the fixed and mobile contacts contact segments with a benzine-moistened rag, and then to slightly lubricate them with pure petroleum jelly.

General maintenance of the machine is essential after approximately 1000 hours of service.



A. Electric defects.

  1. No lamp lights up on the panel when one presses on different keys.

    1. Check the position of the switch for the current of food.

    2. Check if the cut-off switch in the lid in blocked.

    3. If the machine works with on a battery, check if this one is exhausted or badly installed.

    4. When the machine is connected on an outlet, check if it is indeed AC current. With D.C. current, the machine does not function. Check if the cards are correctly connected and if required check the connections of wire in the cards. Also check if there is an break in the power cord.

    5. If the power is from an external 4 to 6 V source, check it, and other connections.


  2. Lamps in the panel burn too weakly.

    1. If using a battery, replace it if required or clean the contacts.

    2. If the machine is using an electrical outlet, set the power selector screw (with the white head) to the corresponding setting.

    3. If using an auxiliary power source (from 4 to 6 V) control its flow.


  3. The light from the lamps is very strong.

    1. If the machine is using an electrical outlet, set the power selector screw (with the white head) to the corresponding setting.

    2. If using an auxiliary power source, check the power which should not be higher than 6 V.


  4. A lamp in the intenal lamp-panel does not light, while the corresponding light in the external lamp-panel does.

    Bad contact with the lamp, either with the casing of the lamp, or with the casing of the panel or with the point of the contact of the lamp. Scrape the place with a knife or a screwdriver. To lubricate lightly the net of the lamp in the panel with a little vaseline.

  5. A lamp of the external lamp-panel does not burn, while the corresponding light in the internal does.

    1. Bad contact with the net of the lamp: See chapter V/A/4.

    2. Bad contact with the connector cable: To check, press on an alphabetical key while moving the cards in the catches and by leading them well to the bottom of those. If, by doing this, the lamp gives a wavering light, check the welding points of the connector cable. If one wire of this cable is defective, one can replace it by one of 2 spares.


  6. By pressing one of the alphabetical keys neither the internal lamp panel, nor that of the external panel, lights up.

    1. Defect of the break contact of a key, in other words when, after each advance of the drum, check the keyboard according to the "Observations" chapter which follows, the same lamp does not light up: Open the lid of the machine, check the contact springs of the lamp which does not light up while driving the corresponding alphabetical key lightly and by possibly curving the contact spring (accessible between the panel to lamps and the comb from the keyboard).

    2. Defect of the make contact of a key, i.e. when by repeating the pressure on the same key no lamp light up: Check the contact under the lever corresponding to the key. To clean this spring with a benzine-moistened rag.

    3. Defect in the drum, i.e. when one actuates and controls the keys one after the other and that after each advance another lamp does not burn on the panel of the machine and the complementary panel: check all the contacts on each disc. A contact perhaps remained hung. To release it, rock it back and forth.


    Observations: To check if all the lamps in the panel light up, or to find one which possibly would not light up, one proceeds as follows:

    On an unspecified position of the drum press the key Q all the way. Then go to it's neighbor, letter W. The first letter, Q, is released only when the letter W is all the way at the bottom. Continue this way with all the letters in the keyboard while going from one line to another, making it possible to check the entire alphabet without advancing the drum.

    If an advance of the drum took place in consequence of a premature release of a key (to check the character-counter!!!) it is necessary to start again with the letter Q. Write down in advance the alphabet from A to Z on a sheet of paper and cross out each one of these letters which appeared on the lamp panel. The letter which remainds makes it possible to discover the defective lamp.

    No other handling of the discs is authorized by troops.

B. Mechanical defects.

  1. By setting the code word a disc on the drum affects a nearby disc:

    1. A disc was inserted the wrong way into the drum: Reset the drum by inserting the double-discs one after the other, with the contact side shaped like a "V" pointed towards the end disc.

    2. Foreign body enters the discs: Disconnect the drum and clean the contacts with a benzine-moistened rag, then lubricate lightly these contacts with pure petroleum jelly.

    3. The drum was not formed correctly according to the "internal key": 
      For a correct assembly to see the chapter III C G, page 23.


  2. The start of the encryption or decryption is correct, but the rest is inintelligible. 

    1. Bad pressure on keys: Press correctly. See chapter III B h, page 22.

    2. One let "jump" the red lever at the time of a repetition: For a correct repetition, see chapter III B I, page 22.

April 3, 1947. Z.A.G. No 117.660 - 1


  1. Hell: A history of Rudolf Hell's inventions is located on this web page.

  2. Creed: In 1900, Fredick Creed invented a way to convert morse code to text, sometimes called the Creed Telegraph System, or the "High Speed Automatic Priting Telegraph System". Information about his company is here.

  3. Note that in this next item, the original document skipped the "j" character.

  4. The French phrase used here is "une caissette portable en bois blindé". The word "bois" means "wood", but the NEMA does not contain any wood. Any ideas?

  5. I translated "compte-lettres" as "character counter". It's the number on the top of the unit that increases each time you press a letter.

  6. I translated "couronnes de propulsion" (crowns of propulsion) as "".

  7. The French word "tambour" means drum, which is appropriate when speaking of a set of rotors on the spindle.

  8. A ratchet wheel. See Mirriam-Webster's definition.

  9. "c.-à-d." probably means "c'est à dire", or "that is to say", or "i.e."

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