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in which the lamp field had been replaced by a printer.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
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but the 25 light bulbs have been replaced by a printing mechanism.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 .
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.
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 .
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
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
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
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.
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
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.
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
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 
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.
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 .
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).
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 .
Click it for a larger view. Any additional
information about the Russian B-211 would be appreciated.
➤ More about the K-37
- Boris Hagelin, 100 Jahre Boris Hagelin 1892-1992
Memoires of Boris Hagelin (German).
Crypto A.G., Crypto Hauszeitung Nr. 11, September 1992.
- Boris Hagelin, The Story of Hagelin-Cryptos
Crypto A.G., Zug, Spring 1981. Based on .
- Bengt Beckman, Arne Beurling and the Swedish crypto program during WWII
2002, American Mathematical Society (English translation).
(Original publication 1996.)
- US Patent US1846105
Hagelin's patent for the B-21 filed in the US in 1928.
- Paul Reuvers, B-21 Dircuit Diagram
Crypto Museum, 2010.
- Boris Hagelin, Die Geschichte der Hagelin-Cryptos
Original manuscript by Boris Hagelin in German language. Zug, Fall 1979.
- TICOM I-58, Interrogation of Dr. Otto Buggisch of OKW.CHI
8 August 1945. Declassified. p. 5.
- VV Babievsky, LS Butyrsky, DA Larin; Soviet cryptographic service 1920-1940
Website Agentura.ru (Russian).
Retrieved June 2012.
- German Patent DE430599
Aktiebolaget Cryptograph, Stockholm, 24 July 1925. 1
- GCHQ, Images of B-211 featured on this page
Crown Copyright. Reproduced here by permission of Director GCHQ. January 2015.
Thanks to Arthur Bauer for bringing this to our attention. November 2012.
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© Crypto Museum. Created: Thursday 15 January 2015. Last changed: Monday, 15 January 2024 - 16:55 CET.