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Hagelin B-211
Electromechanical cipher machine - wanted item

The B-211 was an electromechanical cipher machine with built-in printer, developed by Boris Hagelin at A.B. Cryptograph in Stockholm (Sweden) around 1932. It was a further development of the B-21, especially for the French Army, in which the lamp field had been replaced by a printer.

Unlike many symmetric cipher machine, such as the famous Enigma, the B-211 does not feature poly-alphabetic substitution by means of wired electrical rotors, but a scrambling matrix of 25 keys (5 x 5), just like its predecessor the B-21.

The design is clearly based on the B-21, but the 25 light bulbs have been replaced by a printing mechanism. The image on the right shows the B-211 without its protective cover [10]. The printer is located at the right, with its paper strip running from left to right just above the key­board. Developed by Hagelin, the machine was built under license by LM Ericsson in France.
  
One of the few surviving B-211 machines. Photograph courtesy GCHQ [10].

The machine was developed in 1932 by Boris Hagelin in Sweden in a relatively short period of time, in order to secure the deal with the French Army. About 500 machines were built by L.M. Ericsson in Colombes (Paris, France) and delivered to the French Army prior to the outbreak of WWII [6]. The project became a success, not least because of the (financial) support of Hagelin's father who lived in Paris at the time. He even managed to transfer the profits to Sweden in time.

The French Army was very happy with the machine. When the war was over, they ordered another 100 units, marking the beginning of a long relationship with Hagelin. Eventually, Hagelin would develop a series of power-less portable cipher machines, starting with the very small C-35.


Controls
The image below provides a quick overview of the B-211. At the front is a seemingly normal typewriter keyboard with 29 keys, but note that there are only 25 letter-keys instead of the usual 26 (A-Z). The reason for this is that the 5 x 5 matrix used here, supports only 25 letters. The letter 'W' is omitted, as it can be replaced by 'VV' (pressing the letter 'V' twice).

The cipher mechanism is located at the left and is identical to that of the B-21. It has two commutators at the rear that allow switching between cipher and decipher mode. The 4 cipher wheels are early examples of Hagelin's famous pin-wheels. They can be set by releasing the cipher mechanism with a knob at the left side. The wheels may then be rotated freely.


The space at the right is taken by the printing mechanism of which the print head protrudes the front panel, just above the keyboard. The case of the B-211 is somewhat deeper than that of the B-21, in order to accomodate the motor that drives the printer. This motor is missing from the machine shown here.

Technical description
The design of the B-211 and its predecessor the B-21, is based on an earlier patient by Arvid Gerhard Damm, modified by Boris Hagelin in 1925. It is based on two electrical coding wheels and four so-called pin-wheels that control the stepping of the coding wheels. Although the actual circuit is far more complex, the simplified circuit diagram below shows the situation when the machine is in Ciphering Mode. This part is identical to the cipher mechanism of the B-21.


The keyboard consists of a mechanical matrix and two groups of five electrical switches each. Pressing a key activates one switch in each of the two groups. It also turns on power by activating the ACT-switch for the duration of the key-press. One group of switches is connected to the negative pole of the battery (rows, marked 1 to 5). The other group is connected to the positive pole (columns, I to V).

Each of the signals in then fed through a coding wheel, followed by a programmable matrix. The outputs of the two programmable matrices are then used to active a lamp on the lamp panel matrix. In order to avoid current through all of the lamps, a diode is connected in series with each lamp. In the B-211 shown here, the diodes take the form of an array of selenium diodes probably mounted under the keyboard. In the initial version of the B-21, relays were used instead. The layout of the lamp-matrix is identical to the layout of the keyboard-matrix (QERTY).

Reciprocity
The machine described in the circuit diagram above is not reciproke. For deciphering, a complex system of contacts and wires is used to reverse the operation of each of the coding wheels and matrices. This is mainly done by means of a cleverly designed switching mechanism, controlled by a knob at the left, that is combined with the slide contacts of the two coding wheels.

The image on the right shows a complex system of brushes and contacts that form in fact five cross-switches. When in ciphering mode, the rearmost brush contacts are touching the rings of the coding wheel. The frontmost contacts are disengaged and are instead connected to a fork-contact immediately below it.

The contacts are moved in tandem with the contacts of the other coding wheel, so that they are always switched simultaneously. Contrary to the Enigma, the coding wheels are fixed in place and cannot be removed or replaced.
  
Commutator

Adding the cross-switches to the simplified circuit diagram above, results in the slightly more complex circuit diagram below. This diagram is also available for download at the bottom of this page [5]. The diagram shows the machine in Ciphering mode. Switching to Deciphering, by rotating the C/D knob to the D-position, reverses the path through each of the coding wheel/matrix combinations. The operation of the cross-switches is illustrated at the centre.


Whether or not the selenium diodes are original parts remains to be seen. In 1925, when the B-21 was developed, selenium diodes had not yet been invented. Furthermore, Boris Hagelin describes in the Hagelin Story [2] that he used electric relays in the initial design. It is quite possible however, that the machine was overhauled for diode-operation at a later date.

Russian copy
The success of the B-211 did not go unnoticed. Just before the outbreak of WWII, Boris Hagelin was forced (by the Swedish authorities) to sell two B-211 units to the Russian Embassy. The Russians took the design and copied the machine. At the same time they converted the 5 x 5 matrix into a 5 x 6 one, in order to accomodate more characters. It allowed 30 letters of the Cyrillic alphabet to be used (the full alphabet has 33 letters). They called the machine K-37 [7].

The image on the right shows a top view of the Russian copy of Hagelin's B-211. The design of the cipher unit at the left is nearly identical to that of the B-21. The leftmost cipher wheel has 5 contacts (like the original) but the rightmost one has 6 contacts, resulting in 30 letters.

The printer has been adapted for 30 characters. It has been moved to the center of the machine, with the print head sticking out in the middle, just above the keyboard. With its 30 keys, the keyboard supports the most frequently used letters of the Cryillic alphabet (3 are omitted).
  
Russian copy of the Hagelin B-211

At the right rear is the electro motor that drives the printing mechanism. In front of the motor are 12 relays that are used for driving the rows and columns (5 + 6). The function of the 12th relay is currently unknown. The image above was taken from Boris Hagelin's personal memoires [6]. Click it for a larger view. Any additional information about the Russian B-211 would be appreciated.

References
  1. Boris Hagelin, 100 Jahre Boris Hagelin 1892-1992
    Memoires of Boris Hagelin (German).
    Crypto A.G., Crypto Hauszeitung Nr. 11, September 1992.

  2. Boris Hagelin, The Story of Hagelin-Cryptos
    Crypto A.G., Zug, Spring 1981. Based on [6].

  3. Bengt Beckman, Arne Beurling and the Swedish crypto program during WWII
    2002, American Methematical Society (English translation). p. 31-32.
    (Original publication 1996.)
    ISBN 0-8218-2889-4

  4. US Patent US1846105
    Hagelin's patent for the B-21 filed in the US in 1928.

  5. Paul Reuvers, B-21 Dircuit Diagram
    Crypto Museum, 2010.

  6. Boris Hagelin, Die Geschichte der Hagelin-Cryptos
    Original manuscript by Boris Hagelin in German language. Zug, Fall 1979. pp. 21-22.

  7. TICOM I-58, Interrogation of Dr. Otto Buggisch of OKW.CHI
    8 August 1945. Declassified. p. 5.

  8. VV Babievsky, LS Butyrsky, DA Larin; Soviet cryptographic service 1920-1940
    Website Agentura.ru (Russian). Retrieved June 2012.

  9. German Patent DE430599
    Aktiebolaget Cryptograph, Stockholm, 24 July 1925. 1

  10. GCHQ, Images of B-211 featured on this page
    Crown Copyright. Reproduced here by permission of Director GCHQ. January 2015.
  1. Thanks to Arthur Bauer for bringing this to our attention. November 2012.

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