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Fialka wheels
At the heart of each Fialka machine is a drum with 10 different electromechanical cipher wheels (rotors) that move in an irregular manner when entering a message. Each wheel has 30 contacts at either side and is identified by a letter of the Russian alphabet, as follows:

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

A collection of 10 such unique wheels is called a wheel-set, or just: set. Each wheel is wired differently, and each country of the former Warsaw Pact had its own wheel-set (wired differently for each country). Such a country-specific wheel set is called a series, identified by a number and the letter 'K' (e.g. 3K for Poland). Direct communication between Warsaw Pact nations was strictly prohibited during piecetime and any messages had to be sent via the Russians. Only in the event of war with the West, a common wheel-set (known as the 0K-series) would be released.

Wheels taken from the spindle

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:


The 10 different wheels are placed on a spindle in the order dicatated by the daily key, similar to the wheels of an Enigma machine. A retaining clip is used to keep the wheels locked to the spindle. The spindle is then placed inside the Fialka machine, after which the entry disc and the reflector are locked. After setting the wheels to their initial position, the machine is ready for use.

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. They are known as the PROTON-2 upgrade. 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.

Adjustable wheels (left) and fixed wheels (right)

Fixed wheels
Below are the original wheels that were distributed with the M-125 machines when they were first introduced in 1956. They were also supplied with the first M-125-3 machines when they were released in the mid-1960s. As these wheels are not adjustible, they are called the fixed wheels. The non-metal parts are made of brown bakelite with a fibre-strengthened outer ring with gaps.

Two cipher wheels taken off the spindle

Each wheel has 30 disc-shaped contacts on its left side and 30 spring-loaded contact pins on the right side. With each machine, a unique set of 10 different wheels was supplied, marked with 10 letters of the Russian alphabet as described above (Wheel ID). The number is printed on the right side of the disc; in the example below this is the letter 'A'. As the wheels are wired differently for each country, a series identification (Series ID) is also printed on the right side. In the example below this is '3K', which indicates that this wheel was used with the Polish Fialka variant.

Inside the wheel, the 30 contacts on the left are connected to the contacts on the right in some scrambled manner. This wiring can not be changed in the field. At the outer rim of each wheel are a number of metal pins. These pins control the irregular stepping of the Fialka and are called the Advance Blocking Pins. Each wheel has a different number of such pins at different locations.

The standard cipher wheels (left) and the spare wheels (right)

Each Fialka was supplied with two complete sets of wheels: an operational one and a spare one. The operational set usually resided inside the machine and had black lettering on the index ring. The spare wheels had red lettering and were kept in an metal container inside the dust cover.
The operational wheel set (front) and the spare wheels in an aluminum container The spare cipher wheels in an aluminum container The standard cipher wheels (left) and the spare wheels (right) Standard and spare fixed wheels side-by-side Two cipher wheels taken off the spindle Opening the wheel The inner wiring of a cipher wheel (wiring core) Close-up of the fixed wiring

Adjustable wheels   PROTON-2
In 1978 a new operating procedure for the Fialka was introduced, known as PROTON-2. At the same time a new set of cipher wheels was issued. For each individual country, the new PROTON-2 wheels were prepaired in Russia well in advance of the actual release date. They were shipped in small carton boxes, such as the one shown here, which was discovered in Czechoslovakia.

These new wheels were much more complex than the earlier ones, and can be adjusted in a number of ways. This greatly increases the maximum number of permutations and, hence, the cipher security of the system, without making any modification to the machine whatsoever. In their basic setting, the adjustable wheels are compatible with the earlier fixed wheels. Although the adjustable wheels can theoretically be used in the older M-125 machine, no evidence has been found so far to indicate that this was actually done in practice.

Spare wheels taken from the spindle

The wheels that normally reside inside the machine, have black lettering on the index ring, with one letter in red to identify the wheel (Wheel ID). For example, on wheel 'A' the letter 'A' on the index ring is painted red, as shown in the image below. Inside the dust cover of the machine is a spare set of wheels, stored inside a cylindrical aluminium container. The letters on these spare discs are all red, except for the letter that identifies the wheel, which is black.

On the new adjustable wheels, the letter index ring is now movable, much like the Ring Setting (German: Ringstellung) of the Enigma machine. The ring is locked in place with the index release notch. Secondly, the wiring core can be now removed (see below) and can be re-inserted in 30 different orientations, plus 30 more, if the core is flipped around (side 2 up). Furthermore, the wiring core of a particular wheel can be re-inserted into any of the other wheels as well.
In order to accomodate the removable wiring core, the thick circular spring-loaded contacts of the fixed wheels have been replaced by very thin U-shaped contacts that are made of spring-wire. On the inside of the wheel, the spring-wire is bended in such a way, that it makes contact with the reverse side of the core. The image on the right shows the interior of an adjustable wheel of which the wiring core has been removed.

These contacts have to be handled with care, as they are easily damaged. Spare springs were usually supplied with each maintenance kit.
The spring-contacts inside the adjustable wheel

If the correct core (i.e. the core with the same ID as the wheel) is inserted into the wheel, with side 1 up (i.e. side 1 visible from the left side of the wheel) and the white index line is lined up with the letter A on the index ring, and the index ring is set at the letter A, the wheel is backward compatible with the corresponding fixed wheel. This setting is known as the basic wheel setting.
Original carton box in which the Czech PROTON-2 wheels were distributed Frontal view of the operational wheel set Close-up of the operational wheel set Close-up of an operational wheel Wheels taken from the spindle Fixed flat-faced contacts (left side) Spring-loaded contacts (right side) Close-up of the spring-loaded contacts of a bakelite adjustable wheel
Aluminium can with spare wheel set Spare wheel set in aluminium can Spare wheel set in aluminium can Spare wheels (front) and operational wheels (rear) Spare wheel set Removing a spare wheel from the spindle Spare wheels taken from the spindle Close-up of the spare wheel set
The wiring core removed from a 5K wheel The wiring core removed from the wheel Wiring core removed from the wheel Close-up of a 5K wiring core (wheel K, side 2) The spring-contacts inside the adjustable wheel Inserting the wiring core Inserting core K with the mark at the letter 'A' The ID and the side of the wiring core are printed in white on the side of the core

Disassembly of an adjustable wheel
This image below shows how the adjustable PROTON-2 wheels can be disassembled. Originally, a special tool was supplied to open the wheel, but this can also be done manually by pressing the center disc down with both thumbs, and then rotating it until the center disc comes off. The wiring core can then be removed. Assembly of the wheel works just the other way around.

By flipping the core around, the wiring is effectively mirrored. This greatly increases the maximum number of settings. To make it even more complex, the core can be moved to another wheel, that has its Advance Blocking Pins at different positions. All this was part of the daily key. The Core ID and the side number (1 or 2) are printed in white in the centre part of the core, but also at the outer rim at both sides. This way the Core ID and the side number are always visible, even when the wheel is reassembled again and the metal centre disc covers the text on the core.
Fialka wheel opener Fialka wheel opener Fialka wheel opener Fialka wheel opener Holding the Fialka wheel opener Holding the Fialka wheel opener Fialka cipher wheel with special opener Opening a wheel with a special tool

PROTON-2 key setting
The drawing below shows which parts of the PROTON-2 wheels can be adjusted and how it affects the setting of the daily key. For each day, a small printed card was supplied in a sealed bag. A two-digit number in the top right corner of the card identified the day of the month.

The card further contained 5 lines with 10 Russian characters each. The first line (1) gives the order in which the wheels should be placed on the spindle. Line (2) gives the setting of the index ring. The next line (3) tells us which wiring core should be used in each position, whilst line (4) shows which side of the core should be visible. Finally, line (5) defines the position of the white index line of the wiring core. Once all 5 settings have been carried out, the daily key is set.

Manufacturing differences
There are two known manufacturing variants of the adjustable PROTON-2 wheels. Initially, the non-metal parts of the wheels were made of brown bakelite (phenol formaldehyde resin), one of the first plastics. These wheels are generally known as the brown wheels. When polymer plastics became mainstream, the production process was changed and from then on the non-metal parts were made of reinforced black plastic. These wheels are commonly called the black wheels.

Plastic (left) and bakelite adjustable wheels (right)

In the image above, both types are shown side-by-side. The bakelite wheels (right) have a fibre-strengthened outer rim (i.e. the transport ring with the gaps). With the plastic wheels, the transport ring is reinforced with metal stubs, as is clearly visible in this close-up. More detailed images of the manufacturing differences can be found below. The first four images show the adjustable and fixed wheels side-by-side, whilst the last four images show plastic and bakelite adjustable wheels side-by-side. All types were available with either black or red lettering.
Fixed wheels (front) and adjustable wheels (rear) Adjustable wheels (left) and fixed wheels (right) Adjustable wheels (left) and fixed wheels (right) Adjustable wheels (left) and fixed wheels (right) Plastic (left) and bakelite adjustable wheels (right) Plastic (left) and bakelite adjustable wheels (right) Plastic (left) and bakelite adjustable wheels (right) Bakelite (top) and plastic adjustable wheels (bottom)

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