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Wheels →
Fialka Wiring
The Fialka takes 10 unique cipher wheels. Each wheel is marked with a letter of the Russian alphabet, from A to K as shown below, and a machine should have one of each. The grey numbers printed below the letters are the wheel numbers that we will use in our tables. It is suggested to use these numbers as alternatives for the Russian letters in correspondence.

10 different Fialka wheels, each marked with a letter of the Russian alphabet.

Each wheel has 30 electric contacts at either side. The right side of the wheel is called the input, whilst the left side holds the output contacts. The input contacts are connected to the output contacts in a scrambled manner. As there are 30 contacts, each wheel has 30 possible positions. Each position is marked with a letter of the Russian alphabet on the index ring, in this order:


A collection of these 10 unique wheels is called a set. There are two different wheel-types: fixed and adjustable. The fixed wheels were introduced with the first Fialka machines in 1956, whilst the adjustable wheels were supplied as an upgrade from 1978 onwards. The adjustable wheels are commonly found with the later M-125-3 Fialka models, whilst fixed wheels remained in use with the older M-125 models. Although it is technically possible to use the adjustable wheels on the older M-125 model, no proof has been found so far to indicate that this was actually done.

Different sets of wheels were issued for each country of the Warsaw Pact and their allies. Such different sets are called series. Each series is identified by a number followed by the letter 'K' that is used as prefix to the serial number. All wheels were manufactured, wired and distributed by the Russians. At present, the following wheel prefixes or series are known:

We don't know in which other countries Fialka was used and what prefix was assigned to their wheel wiring. If you have any information that may help us to expand this page, please contact us. Below is the wiring information for the three series that are currently known to us. This wiring is applicable to both the fixed and the adjustable wheels, but please note that the adjustable wheel has to be in its basic setting. This is further explained below.

Russian wheels   68-series
2017 - For a long time it was assumed that all original Russian Fialka machines — that were probably used in all states of the former Soviet Union, or USSR — had been destroyed. In late 2017 however, we received a original Russian M-125-3 machine, complete with the original cipher wheels, which had a 68-prefix. This has enabled us to trace the wiring, which is given in the table below. In this table, the positions of the advance blocking pins are shown in red.

 More about the Russian Fialka

Polish wheels   3K-series
2003 - Over the past few years, a limited number of Polish Fialka machines have appeared on the surplus market. The wheels from these machines all have a 3K-prefix and their wiring is given in the table below. The input contacts are listed on the top row in sequential order. This is the right side of the disc (i.e. the side with the spring-loaded contacts). The contents of the table show the output contact (left side). The positions of the Advance blocking pins are shown in red.

 More about the Polish Fialka

DDR wheels   4K-series
As far as we know, all Fialka machines that were used in the former DDR (East-Germany) have been returned to the Russians and have since been destroyed. So far, no surviving wheel sets have been discovered, but from a photograph in a recovered East-German Fialka manual, we know that the wheels had a 4K-prefix.

 More about the East-German Fialka

Hungarian wheels   5K-series
2014 - For a long time we had no idea that the 5K-prefix was used for the Fialka wheels used in Hungary. In fact, we didn't even know whether the machine was actually used in that country, until we found a complete set of Hungarian 5K wheels during one of our trips through Europe.

 More about the Hungarian Fialka

Czech wheels   6K-series
2005 - Around 2005, Czech Fialka machines started appearing on the surplus market and we were able to trace the wiring of the wheels, which had a 6K-prefix. Please note that both the wiring and the position of the Advance Blocking Pins are different from the other countries.

 More about the Czech Fialka

Common wheels   ?-series
Although each country of the former Warsaw Pact had its own unique set of 10 wheels, it was sometimes necessary for a country to communicate with one of its partners, for example in case of war or during international Warsaw Pact exercises. For such occasions, each country had a sealed box that contained wheels with the correct wiring for each of the adjacent countries.

During peacetime no Fialka communication between Warsaw Pact countries was allowed, except under the conditions described above. If a message ultimately had to be send from one country to another, it had to go via the Russians who, of course, had access to all wheel sets.

When a war with the West was imminent, a common wheel set would be distributed to all Warsaw pact countries. These wheel sets were identified with an unknown prefix and were kept under wraps by the Russians. As far as we know, the common wheels were never truly released.
Click to see more

The image above shows an extremely rare wheel storage case that was used for the distribution of the wheels used by adjacent countries. It is a dark green wooden box with a padded lid. Inside the case are three pre-shaped bays that can each hold a Fialka wheel set in the usual aluminium container. This is closed with normal snap-on locks and has a (green) temper-evident wax seal at the centre. A small metal plate normally protects the seal against transport damage.

Front view of the sealed box
Perspective view of the closed sealed box
Close-up of the wax seal
The opened box (empty)
Close-up of the interior of the box
Typical view inside a box containg some wheel sets
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Front view of the sealed box
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Perspective view of the closed sealed box
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Close-up of the wax seal
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The opened box (empty)
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Close-up of the interior of the box
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Typical view inside a box containg some wheel sets

Further Fialka wiring
For a better understanding of the operation of the Fialka machine, the tables below give the wiring between the various building blocks. These tables may also be useful when repairing a machine or when creating of a computer simulation. More information in the Reference Manual.

Keyboard → Card Reader
The table below shows the mapping between the keyboard and the input terminals of the card reader. Although all characters of the Cyrillic alphabet are nicely sorted on the keyboard's Switch Array, they are connected to the card reader in a different order.

The table above defines the mapping from the keyboard to the card reader. Please note that on the later M-125-3, 20 of these lines are routed via the NumLock switch (30 ↔ 10), which can re-route them in case the Numbers Only mode is selected. The table represents the 30-setting.

Card Reader → Entry Disc
The card reader adds another level of complexity as it allows a substitution matrix to be defined on a punched card. This can best be described as a static wheel (i.e. a wheel that doesn't move) with a user-definable wiring. If no coding card is present in the machine, you must have the metal test triangle present in the drawer of the card reader. This triangle will force the identity matrix, which means that a 1:1 mapping is defined (A → A, B → B, etc.).

Tha table above defines the wiring between the output terminals of the card readers and the entry disc of the drum (German: Eintrittswalze, or ETW).

Below is the wiring of the reflector inside the Fialka (to the left of the drum) for each setting of the mode switch. The reflector is one of the most complex parts of the machine and can not be removed. It has 30 contact points and the wiring is identical for all known machines, as follows:

First of all, it allows a letter to be encyphered as itself. This is done by isolating contact number 13 from the reflector (marked in red). A signal on this line, will cause the coded letter to be overrided by the original letter. As a result, we are now left with an odd number of contacts (29), which means that we can no longer create pairs. To solve this problem, three wires are connected to the so-called Magic Circuit which performs some kind of triangular switching (marked in blue).

The remaining 26 wires are nicely connected in pairs as one would expect from a reflector. A side-effect of the Magic Circuit is that the Fialka partly loses its reciprocity (i.e. the process of coding is no longer fully reversable), and a different table has to be used for coding and decoding mode. The user therefore has to select the proper mode of operation when using the Fialka. Please note that on the M-125-3, 20 wires are routed via the NumLock switch (30 ↔ 10).

When taking the wiring of a Fialka wheel and the position of the Advance Blocking Pins, we have to observe certain rules in order to ensure that everyone interprets the measured data in the same way. As the current comes in from the right, we will call the right side of the wheel (i.e. the side with the spring-loaded contacts) the input. Likewise, the left side of the wheel (i.e. the side with the flat-faced contacts) will be called output. First mark the position of the pins as follows:

  • Identify the wheel by number rather than letter: A = 1 ... K = 10
  • Identify the position on the wheel by number instead of letter: A = 1 ... Й = 30
  • Remove the wiring core from the wheel (adjustable wheels only)
  • Ensure that the letter ring is set to 'A' (adjustable wheels only)
  • Write down the position of each pins, from A (1) to Й (30)
Trace the wiring of the fixed wheels as follows:

  • Start with spring-loaded contact 'A' at the right side of the disc
  • Find the flat-faced contact at the left side to which it is connected
  • Take the next spring loaded contact at the right side (Б)
  • Find the contact at the left side to which it is connected
  • Repeat the above procedure until all 30 wires are traced
The wiring of the removable core of the fixed wheels is traced as follows:

  • Start with the contact at the mark (white line) at side 2
  • Find the contact at side 1 to which it is connected
    (counting counter-clockwise when viewed from side 1)
  • Take the next contact at side 2 (counting clockwise when viewed from side 2)
  • Find the contact at side 1 to which it is connected
  • Repeat the above procedure until all 30 wires are traced
The above procedure will reveal the wheel configuration in the basic setting. This means that the ring is set to 'A', that the matching wiring core is used (i.e. core 'A' in wheel 'A', etc.), that side 1 of the core is visible (from the left side of the wheel) and that the mark of the core (i.e. the white line) is lined up with the letter 'A' on the wheel.

Below are some files that are available for download. Please note that these files are supplied 'as-is'. Crypto Museum can not guarantee the suitability of these files for any purpose whatsoever.

  • XML files for software Simulator authors 0.10 (25 Dec 2017)
    This is a ZIP archive, containing a set of XML files that describe all features of the Fialka and its wheels. These files can be used by software writers when creating, for example, a Fialka Simulator. Includes 68, 3K, 5K and 6K wheel wiring.
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Crypto Museum. Created: Monday 07 July 2014. Last changed: Thursday, 07 January 2021 - 13:01 CET.
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