Basic Fialka cipher machine
The M-125, codename FIALKA
was a Russian
developed during the Cold War by the USSR in the late
1950s. It features 10 electrical coding wheels,
with 30 contacts at either side,
that move in alternate directions.
The machine has a card-reader at the left that acts as an extra (static)
wheel. It consists of a 30 x 30 contact matrix and allows its permutations
to be altered as part of the daily key. The card reader is comparable
to (but cryptographically stronger than) the
plugboard of the Enigma.
Like the Enigma, the electric current enters the wheels from the right via
a static disc (the entry) wheel. The current path is returned through the
wheels by means of a reflector at the left. Unlike Enigma however, on which
a letter can never be encoded into itself, Fialka features a clever
'magic circuit' (German: Dreipunktschaltung)
that does allow a letter to be encoded into itself.
Nation-specific variants were made for the various countries
of the Warsaw Pact. These had keyboards and print heads
that were adapted for the local language. Furthermore, the cipher
wheels had a country-specific wiring, so that during piecetime
the various countries could not communicate with each other
The M-125 contains a paper tape
puncher, a printer and a paper tape reader. Furthermore it has a digital
5-bit data output at the right rear, that can be used to drive a telegraphy
system or a transmitter directly. It can also be used for adding extra
security to the system, by connecting it to the advanced
TEMPEST Power Supply Unit (PSU).
Two different power supply units are known to
have been issued with Fialka machines: a
standard PSU and a
TEMPEST compliant version.
The M-125 was succeeded in the late 1960s by the
M-125-3, which is basically
an improved - backwards compatible - version of the M-125 with support
for extended character sets. Nevertheless, the M-125 stayed in use for
a number of networks, right until the end of the USSR.
The base of the machine (and the internal wiring) was the same for
all countries of the Warsaw Pact, but
for each country a customised version of the Fialka
was issued, identified by a suffix to the model number
(e.g. M-125-MN for the DDR). This involved the layout of the
characters on the keyboard, an extra print head
and the country-specific wiring of the cipher wheels.
So far, the following country-specific variants have been identified:
- East-Germany (DDR)
The M-125 Fialka was a mechanically complex, jet easily controllable,
electromechanical cipher machine. It had only two electrical
connections, one at the left and one at the right.
All controls were conveniently spread over the body of the machine.
After connecting the machine to the Power Supply Unit (PSU), it was switched
ON by placing the ON/OFF switch in the БКЛ.-position.
The 30-character keyboard is located at the front of the machine,
with a black spacebar in front of it. When typing a message, a copy
holder can conveniently be raised to hold the message form.
A ruler holds the form in place and can be used as a pointer
by moving it up and down. At the front right is a paper tape reader
that is mechanically coupled to the keyboard. It is used to play back
previously recorded messages.
To the right of the copy holder is the MODE selector.
The image above shows the machine as seen from the front left
with the copy holder lowered.
At the left of the machine is a drawer that can be opened. It holds
a punched paper card that is part of the daily key settings.
A resettable counter at the front left is used to count the number
of characters that are entered.
At the right rear is a combined printer/puncher.
A three-position lever in the large red circular 'blob' to the right of the
drum, is used to select the required mode of operation. It is called the
MODE selector and is used to select between Coding, Decoding and Plain Text.
The settings are explained in the following table:
The lower two entries in the above table are the settings of the
Print/Punch control lever, that is located to the right of the MODE selector
and is part of the same red 'blob'.
Please note that in Punch mode (ПФ) the printer is also enabled.
This means that the paper tape will contain punched data as well as
printed text. Printing can not be disabled on the M-125.
Set the Print/Punch selector to Print (ПЧ) to disable the puncher.
This setting is needed when narrow 10 mm paper tape is used.
The basic Fialka machine supports 30 different characters
and was designed for the Russian language and the Cyrillic character set.
As Cyrillic has more characters than Latin, the usual 26 characters were
not sufficient. In order to avoid mechanical complexity of the electric
wheels, the 30 most frequently used Cyrillic characters are used.
These are the following characters:
А Б В Г Д Е Ж З И К Л М Н О П Р С Т У Ф Х Ц Ч Ш Щ Ы Ь Ю Я Й
On each Fialka machine, regardless the country in which is was used,
these 30 characters are always at the same position on the keyboard and
on the print head. As the same characters are used to identify the position
of a cipher wheel, we will use these Cyrillic letters as the reference.
On the international version of the M-125,
it is possible to switch between Russian and Latin.
For this, two letters are printed on each key top: a Cyrillic one in green
(left) and a Latin one in red (right). The position of the Latin characters
varies per country. Numbers were not present on the keyboard and had to
be typed in full (e.g. in German: 'dreisieben' instead of '37').
The M-125 uses 10 cipher wheels, each of which has 30 flat-faced
electrical contacts at one side and 30 spring-loaded contacts at the other
side. The 30 positions of each wheel are marked with the 30 letters of the
Russian alphabet, in clockwise order (when viewed from the
А Б В Г Д Е Ж З И К Л М Н О П Р С Т У Ф Х Ц Ч Ш Щ Ы Ь Ю Я Й
Each of the 10 cipher wheels is wired differently and has a number of
pins at the outer rim that are used to control the stepping of the
wheel next to its neightbour. The number of pins and their position are different
on each wheel. Each of the 10 wheels is identified by a letter of
the Russian alphabet which is engraved in its right side.
The following 10 letters are used:
А Б В Г Д Е Ж З И К
The 10 wheels are mounted on a spindle
and are held in place by a retaining clip.
The spindle is then placed inside the machine.
Each machine came with
two identical sets of wheels:
one inside the machine (the operational set)
engraved with black letters,
and a spare one with red engraved letters
in an aluminium container
inside the dust cover. The wheels were numbered sequentially.
The image on the right shows the operational wheels,
two of which (K and E) are removed from the spindle, with the
spring-loaded contacts (i.e. their right side) facing upwards.
The И-wheel is just visible at the right end of the spindle.
Each wheel is wired differently in a fixed pre-determined pattern
that can not be altered in the field. The wiring can be accessed by
removing the metal disc at the left side of the wheel, using a
special tool or just by pressing and rotating the disc with the fingers.
The wiring was different for each country of the Warsaw Pact.
When looking at the wheels from the top of the machine, the odd wheels
move towards the front of the machine, whilst the even wheels move towards
the rear. Wheels 2 and 9 are always advanced when a key is pressed.
Stepping of the other wheels is controlled by the position of the
notches or pins at the rim of another wheel.
This is illustrated by the drawing below:
In principle, all wheels can make a single step in each key-press,
but its stepping can be inhibited by its controlling wheel.
Wheel 2 controls the stepping of wheel 4. If a pin is present at a
certain position, it inhibits the stepping of wheel 4. For this reason
the pins are also known as 'advance blocking pins'.
In the same way, wheel 4 controls the stepping of wheel 6, and so on.
For the odd wheels, wheel 9 is the driving one. It controls wheel 7
that in turn controls wheel 5, etc.
➤ Wheel stepping in more detail (coming soon)
In 1978, the standard fixed wheels were replaced by the
far more advanced adjustable cipher wheels as part of the PROTON-2
directive. This allowed the wheels cores to be reversed,
inserted in different positions and in different wheels.
Although these PROTON-2 wheels could perfectly well be used inside
the standard M-125, we have never found any proof of this.
All M-125 machines that have survived have been found with the older
fixed wheel sets.
As far as we know, the PROTON-2 wheels were only issued with the later
M-125-3 machines. With the wheel cores
in their neutral position, these wheels are backwards compatible with
the older fixed wheels, allowing communication between the
two Fialka models.
➤ The cipher wheels in more detail
➤ Wheel wiring in more detail
The M-125-3 has a card reader
that adds an extra layer of permutations
to the machine. The card reader is located at the left side of the machine
and consists of a drawer that gives access to a 30 x 30 contact matrix.
In many respects it can be seen as a non-moving programmable wheel.
Lower the metal bar that protects the reader and firmly pull out
the drawer that holds the card.
As the Fialka uses a reflector, just like Enigma's Umkehrwalze,
the current passes the card reader twice.
In practice the punched
card was part of the daily key and was changed every 24 hours.
It was made of paper that was so thin that it easily got ripped, so that it
could not be used twice.
➤ The key cards in more detail
➤ The card reader in more detail
Unlike the WWII German Enigma machine, that presented its output on a panel
with 26 lamps, the Fialka can print its output directly on a paper strip that
could be used directly in a telegram. In addition, the machine could also
punch the message into a standard 5-level teleprinter tape.
The combined printer/puncher is located at the right rear and is visible
through a hole in the top lid of the machine, just behind the copy holder.
The printer consists of a rotating print head with one or two rows of
characters. A lift mechanism determines which of the two rows is used.
The paper strip moves behind the print head from right to left and leaves
the machine at the left.
In between the print head and the paper strip is a standard typewriter-style
ink ribbon. When the required character is facing the paper strip, a hammer
is released from the rear of the paper.
The hammer momentarily pushes the paper strip (and the
ink ribbon) against the print head, causing the character to be printed.
When using standard 5-level paper tape, the integrated puncher stores
the message on the paper strip by punching out the required holes,
whilst the same message is printed as text at the position of the
sprocket holes (albeit at an offset).
The Fialka accepts two paper sizes. In addition to the standard 5-level
teleprinter tape, it is also possible to print the text on a narrow
10 mm paper tape. This tape is entered from the rear of the machine and
uses a different path to the printer, bypassing the puncher.
When this type of paper is used, the tape guide (behind the ink ribbon)
has to be adjusted accordingly. When pre-gummed tape was used, it could
directly be glued onto a telegram sheet or message form.
➤ The printer in more detail
The M-125-3 has a fully integrated paper-tape reader that accepts standard
5-level teleprinter tape in the specific Fialka encoding standard.
It is located at the front right of the machine
and is mechanically coupled to the keyboard.
It can be used to play back previously created messages.
The image on the right shows the tape reader. A small lever, just below
the red button, allows the reader to be opened after which a tape can be
inserted. After closing the reader, the message is played back by pressing
the ПУСК button (start).
When running, the tape reader directly actuates the five coding rods
underneath the keyboard, as if the keys were actually pressed.
After the green ПУСК button is pressed,
the tape runs until the red СТОП button (stop) is pressed
or a NULL character (00000) is encoutered on the tape.
The keyboard is then decoupled again.
Although it was technically possible to connect the Fialka directly to a
transmitter using the DATA output socket,
this was not recommended. If the machine was
accidently left in the О-position (plain text)
instead of the З-position
(coding), the original message would be sent in clear.
In order to avoid this risk, it was recommended that a message was first
encrypted on a punched paper tape, using the built-in puncher, and then
tested by reading it back through the reader using З-mode (decipher).
If this did not result in garbage, the tape would be send in clear.
The advantage of this method was that the encrypted tape could also be sent
by separate tape transmitter that did not necessarily have to support the
same 5-level encoding scheme.
➤ The tape reader in more detail
The M-125 has a character counter at the front left that is used
to count 5-letter groups. The counter is reset by pressing the large
push-button at the front of the machine's base. The rightmost digit
(marked with a red border)
is used counts the characters and wraps around at five (1-5) whilst the
remaining 3 digits are used to count the number of 5-letter groups.
Counting the number of 5-letter groups was an important part of the procedure
as cipher text telegrams were generally sent this way.
When placing the dust cover over the machine and locking it up,
a bracket mounted to the front of the dust cover ensures
that the large reset button is pressed before the case is closed.
This is done to ensure that the counter is always set to zero when the
machine is unused. This way the counter reveals no information about the
latest message that was (de)coded. This counter is also present on the
Counters of this type were commonly used on other Russian cipher machines
of the 1960s, 70s and 80s as well, and were probably made by the same manufacturer.
As an example: the
cipher unit of the M-130 (Koralle)
has a nearly identical (black) counter mounted at the top right.
The M-125 was originally supplied with a number of accessories,
tools and spare parts, some of which were stored inside the dust cover.
Below an overview of the various accessories that were available.
Click any of the thumbnails below to find additional information
about the item.
When they were released by the factory, each Fialka machine came with its
own hand-written checklist. It shows which items were originally supplied
with the machine when it was issued to the users in the field.
Some of the items have been found by collectors over the years, but
a few of them remain a mystery to this day...
➤ More information
The Fialka is an extremely compact machine, with many features efficiently
cramped into a small space, and the same can be said of the dust cover that
slides over the machine from the top and is retained by two locks at the front
and two at the rear. It can be carried with a grip at the front.
The rectangular dust cover protects the machine agains dust, water
and other hazards, so that it doesn't get damaged during transport.
It is also used to store some of the frequently used accessories.
With a clever use of the limited available space, the designers have
succeeded in storing the paper reel holder, the paper chad box, the test
reflector, two spare print heads, the crank and an aluminium can with a
spare set of cipher wheels. The image on the right shows how these are
stored. The crank is not visible in this image; it is stored at the
The dust cover is nearly identical to that of the later M-125-3.
The dimensions are the same and most accessories are stored in the same
place, with the exception of the paper chad box
that is stored over the spare wheel container.
More about each accessory below.
The dust cover also serves as a safety measure to avoid giving away
strategic information. At the front of the cover is a small metal bracket
that mates with the counter reset button in the bottom of the case.
When re-fitting the dust cover, the counter reset button has to be
pressed, before the cover can be closed. This ensures that the counter is
always reset when the machine is stored, so that it no longer reveals
information about the length of the latest message that was created.
When using the machine to store messages on a 5-level punched paper tape,
the small circular punched-out pieces of paper leave the machine through
a small channel at the right rear, just in front of the Data socket.
The chad is collected in the paper chad box that is attached at the right.
The paper chad box is normally
stored inside the dust cover,
over the aluminum container with the spare wheel set.
It is held in place by a
spring-loaded metal stub
that is attached to the side of the dust cover.
Pull the spring upwards to remove the chad box.
Now simply hang the box over the two screws
at the side of the machine.
Once the box is in place, the paper chad outlet channel should be
extended to avoid spilling the paper chad aside the box.
When typing on the keyboard whilst a wide paper tape is present,
any paper chad will now fall into the chad box.
When using the printer and or the tape puncher, the paper tape has to be
fed in from the right of the machine. A suitable tape feeder is
stored inside the dust cover.
It consists of a square matal plate with several guides
and a spool at the center. The spool accepts a fresh reel of paper tape.
Keep turning the capstan, until the paper tape becomes
visible at the tape outlet
at the left side of the machine.
Fialka accepts two different paper sizes: wide and narrow.
The most commonly used paper tape is the wide variant that is used for
creating 5-level punched paper tape.
This is the same paper that is used in
Europe and in the US for storing teleprinter messages
With Fialka, this paper can be used to punch 5-level data, print text
or both. Alternatively, it is also possible to use narrow 10 mm paper
tape for text only. When this tape is used, the puncher has to be
swiched off by setting the print/punch selector set to ПЧ.
Furthermore, the paper guide behind the ink ribbon has
to be adjust for the narrow tape.
Each Fialka machine is supplied with a
small hand crank that is usually
stored inside the dust cover,
in the corner behind the paper tape feeder.
The crank is made of hardened steel and has a bakelite grip.
It can be inserted into a hole in the right side of the body of the
machine where it is engaged with the main non-ratating driving axle.
It can be used to advance or step-back the position of the wheels
as part of the operating procedures or for the correction of mistakes.
As a troubleshooting aid for a malfunctioning machine,
a test reflector was supplied that could be mounted instead of the
cipher wheels, effectively eliminating the wheels.
The test reflector was usually stored on a small axle
inside the dust cover and was held in place by a retaining clip.
In order to use the test reflector, two retaining clips are needed:
the one that was used to retain it inside the dust cover and the
one that normally retains the wheels on the spindle.
Especially for use of the test reflector, the spindle has an extra
rig engraved towards the right. The tet reflector is placed between
the two rigs and held in place by the two retaining clips.
The spindle is then mounted inside the machine in the usual manner,
as shown in the image on the right. The white line of the test
reflector has to line up with the white dot on the entry disc.
The test reflector connects the contacts of the entry disc together
in pairs: 1-2, 3-4, 5-6, etc., and effectively eliminates the cipher wheels
and the reflector from the cryptographic algorithm. When the machine is
set to Coding or Decoding Mode (the MODE selector in the 'З'
or 'Р' position) and the metal test triangle is placed in the card reader,
it is now possible to trace the electric current from each key through
the card reader, the entry disc and back, through to the printer.
Each Fialka machine came with two full sets of rotors: an operational one
that resided in the machine, and a spare one that was stored in an aluminium
can. In order to distinguise between the two sets, the letters on the rim of
the operational set were painted in black, whilst the letters on the spare set
were red. The letter identifying the wheel was painted in the alternative
The image on the right shows a complete spare set as it was supplied
with the Polish variant of the M-125-3. The wheels have red lettering with
one letter (the letter identifying the wheel) in black. The wheels all have
identical serial numbers (in this case: 1391) with a '3K' prefix, indicating
that the wheel have Polish wiring.
The spare wheels were normally stored in a aluminium container that was
kept inside the metal dust cover, where it was retained by a metal strip.
The red wheels would only be used in case the operational wheels were broken
or needed maintenance, which is why the quality of the red wheels is often
The spare wheels were wired identically to the operational ones so that they
could be used immediately in case of an emergency. When not in use, the
wheels were all set to their basic position (i.e. the rings set to 'A'
and the cores with side '1' up) and were placed on the spindle in the order
of the alphabet, so that no information about a previous key was revealed.
Having a spare wheel set was also useful in case the cryptographic key was
changed more often (e.g. twice each day). It allows one set to be prepared
for the new key well in advance, so that it can be swapped quickly. This
minimises the time the machine is 'off-line'.
➤ The wheels in more detail
Each Fialka machine was supplied with a toolkit that was used for daily
maintenance and small repairs. The toolkit consisted of an (army) green
canvas wallet with several screwdrivers, wrenches, pins and hooks.
Although a toolkit was supplied with every machine, not many of them
have survived, making them into desired collector's items.
➤ More information
In addition to the toolkit, the Fialka was also supplied with a small
wooden box with spare parts and accessories, or in Russian:
Запасные части И Принадлежности,
or ЗИП (Latin: ZIP).
The spares kit contains mechanical, electrical and electronic parts,
a tape moisturizer, a spare axle, retaining clips and much more.
➤ More information
Apart from the toolkit, an oil can was supplied for maintenance.
It was used to oil the moving parts of the machine, such as the axles,
the bearings and the rotor spindle.
The image on the right shows the oil can that was supplied with
each Fialka machine.
➤ More information
Each country of the Warsaw Pact had its own version of the User Manual,
written in the local language. The manual
explained the operation of the M-125-3, its maintanance
and the cipher procedures to be followed.
The image on the right shows the East-German version of this
manual, which was known in the DDR as A 040/1/321 .
The image on the right shows the standard PSU, of which two manufacturing
variants exist. It is the most common PSU that was used with Fialka machine
and was also issued with the later M-105 (Agat) cipher machine.
The standard PSU allowed the Fialka machine to be powered from a wide
range of mains AC voltages as well as from a 24V DC network.
➤ More information
Polish Fialka machines (M-125-3MR2) were issued with a very
sophisticated stabilized Power Supply Unit (PSU) that contained
extra circuitry to improve overall cipher security by adding extra TEMPEST
➤ More information
For setting up a Fialka machine in the dark and for maintenance and repair,
a small 24V service lamp was supplied as part of the
spares kit (ZIP).
It consisted of a bakelite grip, a
metal reflector and a 24V car lamp. At the end of the cable was a 2-pin
plug, similar to a mains wall plug (which is probably why so
many lamps are broken).
The service lamp was connected to the 24V outlet of the Fialka PSU,
'piggy backed' to the Fialka power cable
of the standard PSU, or to the
dedicated socket of the Tempest PSU.
Each Fialka machine was issued a thin metal triangle that could be
placed in the drawer of the card reader, instead of the key card.
At the end of the day or session, the Fialka was set to its basic
position and the key card was removed and destroyed.
The metal triangle was then placed in the card reader. It forces
the identity matrix (A → A), so that the machine
can be used in plain text Mode.
➤ The test triangle in more detail
In some cases the Fialka was used to print the decoded output
directly to narrow pre-gummed 10 mm paper tape, so that the
message could be glued on to a message form, just like a telegram.
In such cases the tool shown in the image on the right was used
to moisterize the pre-gummed tape in order to activate the glue.
➤ The tape moisturizer in more detail
In addition to the Spare Parts and Accessories Box (ZIP) shown
above, various other parts and building blocks were available for
an authorised repair centre.
Apart from the usual mechanical, electrical and electronic
components, complete building blocks were available, such as the
5-bit encoder diode matrix,
the puncher driver and the
famous magic circuit.
The M-125 can read and punch standard 5-level paper tape, just like many
western telegraphic devices of the era, but uses neither the
nor its Russian variant – MTK-2 –for this.
Instead, the machine uses a proprietary encoding scheme that was only used
for Fialka and for the later M-105 (AGAT)
one-time tape machine.
The 5-bit alphabet is illustrated in this diagram:
With 5 holes it is possible to create 25 = 32 different combinations.
30 of these are used for the standard 30 characters that are available on
the keyboard. The two ramaining positions are taken by the SPACE character
(10001) and the NULL character (00000), which is also known as STOP.
Although the circuit diagram of the M-125 is very complex, its operating
principle is similar to, but more advanced than, the
that was used by the Third Reich during WWII. The extra complexity
was added to circumvent certain cryptographic
weaknesses of the Enigma.
Let us first consider the above block diagram of the Enigma.
It has 26 keys that operate 26 switches. The current from the
battery is passed by these keys through the plugboard (German: Steckerbrett)
onto a static entry disc (German: Eintrittswalze, or ETW).
From the ETW, the current is passed through the cipher wheels
until it hits the reflector (German: Umkehrwalze, or UKW).
The UKW returns the current back through the wheels, the ETW
and the Steckerbrett, after which it arrives at the lamp panel
where the lamp of the encoded letter lights up. This is the output.
The operating principle of the M-125 is similar, but the plugboard
has been replaced by a card reader that offers a
stronger encryption by providing a non-self-reciproke permutation.
The keyboard (at the right) is used for the input. It consists of 30
one for each key. Furthermore, the keys are mechanically encoded into a
5-bit digital code
(similar to Baudot).
When typing, the current from the
30 contacts is passed to the card reader at the top right.
From the card reader, the current is passed via the static entry disc,
through the 10 cipher wheels.
After the current arrives at the reflector on the left, it is returned
through the 10 wheels, the entry disc and the card reader,
until it arrives at the 5-bit encoder (bottom right),
where the 30 lines are converted into a 5-bit code
(similar to, but different from Baudot)
for the printer.
➤ Block diagram in more detail
The use of a reflector makes the machine symmetrical, which means that
the same settings can be used for encoding and decoding. A major drawback
however, is that a letter can never be encoded into itself. This was considered
weakness of the Enigma cipher machine.
In the Fialka, this is solved by adding a clever electronic circuit
to the reflector, to ensure that a letter can be encoded into itself.
This is done by taking 4 wires out of the reflector (i.e. two pairs).
One of these wires is used as the 'letter-can-be-itself' signal and is
sent back to the keyboard. The remaining three wires are combined into a
binary rotator. In the German Fialka literature, this circuit is called
Dreipunkschaltung (three-point circuit), but we have dubbed it
The effect of the Magic Circuit is that each letter has a 1:30 chance of being
encoded into any other letter, making the machine cryptographically
stronger than the Enigma.
A side-effect of the binary rotator however, is the the
machine is no longer fully symmetrical. This is solved by adding a
Mode Switch (coding/decoding) that simply swaps two of three lines
of the binary rotator.
➤ More about the Magic Circuit
The keyboard is an extremely complex mechanical assembly. It consists
of 30 keys divided over three rows. When pressing a key, a lever will
actuate the corresponding contact in an array of 30 switches that is
mounted behind the keyboard. It is illustrated in the drawing below.
The contacts are arranged in the order of the Russian alphabet.
An extra switch is added for the spacebar.
Pressing a key also actuates one or more rods, five of which are
mounted from right to left underneath the keyboard, where they drive
five electrical switches. This way the rods
mechanically convert a key (1 of 30) into a 5-bit digital code
that can be used to drive the printer.
The interior of the M-125 can easily be accessed by loosening
two large bolts
in the top of the cover (for one the top lid should be opened),
and a small screw at the front,
just below the keyboard. After that,
the cover can lifted upwards, revealing the complex interior.
The images below should give a good impression of the various parts of
this extemely well-built machine.
The machine can roughly be divided into three sections: the keyboard
at the front, the cipher wheels at the centre and the printer/puncher
at the rear. The card reader is hidden underneath the cipher wheels
and is accessible via a drawer at the left.
Alhough the machine has a highly modular construction, the various
parts are mechanically intertwined in several areas.
All parts are mounted to the base plate (i.e. the bottom shell of the
machine), which acts as a reference for the mechanical adjustment of
some parts. Some axles and pawls are permanently fitted to the base plate
to act as a mechanical interface between certain parts of the machine.
The electrical timing of the machine is generated by an
at the left side of the machine, close to the main spindle.
This contact is actuated by a notched disc that is driven by
the main motor axle. This pulse also acts as the STROBE for the
digital 5-bit data output.
At the front of the machine is the keyboard, which has a complex mechanical
structure of metal arms, pawls and rods underneath the keys. Each key actuates
one of the contacts of an array of switches that is mounted behind the keyboard.
The rods below the keys are also used to mechanically generate a 5-bit digital
code. The code is converted into electrical signals by means of 5 switches
that are mounted in a small metal enclosure to the left of the keyboard.
To the right of the keyboard is the tape reader that is mechanically coupled
to the keyboard. It directly drives the 5 rods underneath the keyboard,
in such a manner that it mimics the operation of the keyboard. This means
that it drives the 30 individual key contacts as well as the 5-bit encoder
to the left of the keyboard.
The tape reader is driven by an axle that is part of the base plate assembly.
When the user presses the green START key (ПУСК), the tape reader is coupled
to this axle and starts reading the paper tape that is inserted at the front.
The tape runs until the user presses the STOP key (СТОП) or a NULL character
is encountered on the tape (00000), at which point the tape reader will be
decoupled from the driving axle. The alignment of the tape reader is
extremely critical and many of the adjustment are sealed (yellow).
The center part of the machine is taken by the wheel stepping mechanism,
which becomes visible after removing the drum (i.e. the spindle with the
10 cipher wheels). It consists of two sets of transport-combs: the upper
one for the stepping of the odd cipher wheels and the lower one for the
stepping of the even cipher wheels.
When the motor is running, this mechanism is at rest, but as soon
as a key is pressed, it is mechanically coupled to the main driving axle,
causing a single step of the wheels. After one full revolution of the axle,
it is decoupled again.
Wheels 2 and 9 are advanced on each key press. The short metal pins at
the other rim of the wheels (sometimes referred to as the notches) control
the stepping of the over-next wheel. The presence of a pin inhibits the
stepping of the wheel two places further. In other words: wheel 2 controls the
stepping of wheel 4, wheel 4 controls the stepping of wheel 6, and so on.
If a pin is absent on one wheel, the wheel two places further will
also make a step when a key is pressed. Of the odd wheels, wheel 9
controls the stepping of wheel 7, wheel 7 controls the stepping of
wheel 5, 5 controls 3 and so on.
The output of the machine is available in three different streams:
as a punched paper tape, in printed form and as digital signals,
all of which is controlled by the printer/puncher mechnism at the
rear right. The printer is driven by the output of a diode matrix
that converts the 30 output lines into a 5-bit digital data signal.
The diode matrix itself is hidden in the bottom section of the machine,
below the mechanical parts. The 5-bit data signal is used to drive
5 solenoids that are located in a metal enclosure at the back of the
printer/puncher mechanism. The solenoids in turn drive the five punchers of the
tape puncher and also control the point at which the hammer of the printer
In addition to this, the output is also available electrically from the
brown 10-pin socket at the right rear of the machine. This signal can be
used to drive external telegraphic equipment directly. It can also be used
for transmission by connecting the R-590A (Rus: Р-590А) interface.
When the machine was used in combination with the advanced Power Supply Unit
(PSU), which was the case in Poland, this output is used to drive the
Electronic Counter Measures that are present in the PSU. It prevents an
eavesdropper from obtaining information by tapping the power line.
The machine is mechanically driven by a 24V DC motor, which is
located at the rear left of the machine. The image on the right shows
the rear of the machine with the grey motor at the right.
When the machine is switched ON, the motor runs continuously until
it is switched OFF again. If a machine hasn't been used for some time,
it is possible that the grease has dried up, preventing the motor
from starting. In such cases it might help to rotate the kurdled knob
at the bottom centre in the direction of the arrow.
Ensure that the machine is off when you do this.
Positions of the serial number
The serial number of the Fialka was printed on a small serial-number
badge that was mounted at the front of the machine, just below the
keyboard. Unfortunately, this badge has been removed from most machines
as part of the demilitarization process. Nevertheless it is possible to
retrieve the serial number of a machine, as it is engraved in a number
of parts inside the machine as well. The following locations are known:
About 10 years after the introduction of the M-125, the machine was
succeeded by the more advanced M-125-3Mxx,
which is built on the same chassis. The newer
machine can easily be distinguised from the older M-125, as most of
them (except for the Russian version)
have square key tops, rather than
rounded ones. At the rear behind the printer, it has an extra MODE selector.
➤ More information about the newer M-125-3.
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© Crypto Museum. Created: Monday 12 May 2014. Last changed: Saturday, 06 March 2021 - 15:58 CET.