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Typex   BID/08
Wheel-based cipher machine

Typex was a wheel-based electromechanical cipher machine, developed in the UK in 1934 by Wing Commander O.G.W. Lywood. It is the British variant of the commercial Enigma machine [1]. After the initial prototype in 1935, the first production batch of 29 Typex Mark I machines 1 was delivered to the RAF in early 1937, soon followed by the bulky but more versatile Typex Mark II, which was used throughout World War II. Typex is sometimes written as Type X or TypeX. Later variants of the machine were also known by their BID designators 2 : BID/08/2 and BID/08/3.
 
Some nice examples of Typex machines can be found in the Bletchley Park musem (UK). The image on the right shows a typical Typex Mark 23 which was used during WWII. It is an adaption of the standard Typex Mark II and Mark 22, and was used for many years after the war was over.

The Mark 22/23 shown here was modified to increase its security and to make it compatible with the German military Enigma machine. Once the German messages were broken with help of the Bombe machines, the intercepted messages were decrypted manually using these machines.
  
Typex Mark 23

The modified Typex Mark 22 (BID/08/2), appeared relatively late in the war and had an extra plugboard at either side of the keyboard. Compared to Enigma, the standard plugboard was more versatile as it allowed each letter to be swapped with every other letter, rather than swapping them in pairs like on Enigma. Some Mark 22 machines were later modified into a Combined Cipher Machine (CCM), to allow the British to exchange secure messages with the Americans.

In the UK, Typex remained in service until the mid-1950s, after which they were replaced by more modern encryption systems, but in other countries they were used well into the 1960s. The Royal Canadian Navy replaced their Typex and CCM machines by the KL-7 in 1962, whilst the Canadian Embassies used them until 1968 [3]. Although all Typex machines were decommissioned many years ago, they are rarely found in museums and very few of them have landed in private hands.
 
  1. The machine was originally dubbed RAF Enigma with Type X attachments. The designator Typex Mark I was assigned when the Typex Mark II was introduced.
  2. BID means British Inter Departmental. Systems with a BID designator are generally used by more than one single governmental agency or department. (More...) Note that the higher BID/08 numbers are used for the Rockex cipher machine, (e.g. BID/08/05).

Typex Mark 23 Typex mark 23 with main cover removed Typex interior A full set of 4 Typex wheels Printer seen from the front Typex keyboard

 
Features
Although there are several different models of the Typex machine, we will look more closely at the Mark 23 variant in the description below, as it is the most complete version of the original Mark II. At the front is the keyboard, which consists of three rows of keys plus a spacebar.

Immediately behind the keyboard is the rotor cage which has room for five cipher wheels. These two items (keyboard and rotor cage) are the actual cipher machine, which is a copy of the Enigma. It has an entry disc and a reflector with five cipher wheels in between, two of which are static.

Typex Mark 23 with the top cover removed

The area behind the rotor cage holds the driving gear or actuator. It is driven from the rear by a motor and provides the timing for all parts of the machine. The two large black cylinders at the left and right are the printers for plaintext and ciphertext respectively. They print to a paper strip.

The 32-pin Strowger socket to the left of the keyboard is for connection of a plugboard that allows the reflector to be rewired. This feature was introduced on the Mark 22 variant and was not present on the original Mark II. The 33-pin Jones socket at the right side of the keyboard, allows a single-ended plugboard to be inserted between the keyboard and the entry disc, much like the Enigma plugboard. These two modifications allowed the Mark 22 to simulate Enigma I.

The image above shows four vertical mounting posts: one at either side of the rotor cage and two towards the rear. These posts were only present on the Mark 23, which is actually a modified Mark 22, and allowed the machine to be converted into a Combined Cipher Machine (CCM).
 
Operation
The image below shows a simplified diagram that explains how the scrambler of the Typex machine actually works. At first glance, the machine is quite similar to the commercial Enigma machine. At the right is the entry disc and a the far left the reflector, each with 26 contacts.

Typex scrambler as shown in the Maintenance Manual [9]

In between the entry disc and the reflector, are five cipher wheels of which the rightmost two are static (i.e. they can be set, but they don't move during encipherment). The leftmost three wheels are controlled by a stepping mechanism that is similar (but not identical) to the stepping unit of the Enigma. On the Typex Mark 22, a plug board was added to allow the reflector to be rewired in the field, similar to the Enigma's Umkehrwalze D (UKW-D or Dora). Another feature of the Mark 22 was the addition of a plugboard that was inserted between the keyboard and the entry disc.


Simplified Enigma circuit diagram

The plugboard of the Typex Mark 22 is similar but not identical to the Enigma Steckerbrett. In order to understand the difference between the two systems, we will first look at the simplified Enigma circuit diagram above. On the plugboard, the letters are always swapped in pairs by means of a 2-wire cable with a 2-pin plug at either end. Each plug has a thick and a thin pin.


Simplified Typex Mark 22 circuit diagram

On the Typex Mark 22 and the later Mark 23, a single-ended plugboard is used, which is not restricted to letter pairs like on Enigma. This means that any letter can be connected to any other letter as shown in the simplified diagram above. As a result, the Typex plugboard allows more permutations than the Enigma plugboard, but is still backwards compatible with the Enigma one.
 
Wheels
The wheels of the Typex closely resemble those of the German Enigma machine. Each wheel has 26 letters around its circumference and has 26 contacts at either side. Each wheel has a thumbwheel that is used to alter the start position, and is driven by a saw-tooth ring at the right.
 
The image on the right shows a full set of 5 Typex rotors as they were shown by David White at the Enigma Reunion 2009. In order to improve reliability, each contact was doubled [1].

Typex is a 5-wheel machine, of which the first two rotors from the right remain static during encipherment (although they could be altered manually). In order to cause more frequent wheel-turnovers (irregular stepping), multiple notches were present on the wheels (e.g. 5, 7 and 9). This feature was also present on the Zählwerk Enigma, but not on the Service Enigma.
  
A full set of 4 Typex wheels

When unused, the wheels were usually stored inside a wooden storage box. Some types of Typex wheels had a removable wire-core. It allowed easy changing, swapping and testing of the wheel wiring in the field. The rightmost image below shows the manufacturing stages of the wire-cores.
 
A full set of 4 Typex wheels Another view of the 5 Typex wheels Typex entry wheel (static) Spring-loaded contacts Wooden box with 5 Typex wheels Typex wheel cores displayed by CGHQ in 2009. Photograph courtsey Kevin Coleman [2].

 
Models
The following Typex models are currently known:
 
  • Typex Mark I
    This is the initial design of the machine that was based on the 1935 prototype. The first batch of 30 machines was delivered in early 1937. This machine was initially known as RAF Enigma with Type X attachments. The designator Typex Mark I was assigned later when the Typex Mark II was introducted. It was connected to a standard teletypewriter.

  • Typex Mark II
    Avanced version of the Mark I that incorporates two printers: one for the plaintext and one for the ciphertext. The first batch of 350 machines was ordered in June 1938. The machine was adopted by the RAF, the Army and other goverment departments. It is the most widely used Typex model that was produced in large quantities during WWII by Powers-Samas [10]. The machine handles 300 characters per minute.

  • Typex Mark III
    This is a hand-operated portable model that used the same cipher wheels as the Mark II and has an operating speed of 60 characters per minute. An optional motor drive attachment was available to allow automatic operation.

  • Typex Mark VI
    Yet another portable variant that weights 30 pounds and measures 20 x 12 x 9 inches. It is less deep than the Mark III, but wider, and uses different cipher wheels.

  • Typex Mark VIII
    Special variant based on the Mark II design, with a morse perforator fitted.

  • Typex Mark 22 - BID/08/2
    Typex Mark II with two plugboards for improved security. The leftmost plugboard is actually a rewirable reflector (similar to Enigma's UKW-D), whilst the rightmost plugboard is similar (but not identical) to Enigma's plugboard. The name 'Mark 22' was derived from 'Mark II' and 'variant 2'. Many Mark II machines were converted into Mark 22 machines.

  • Typex Mark 23 - BID/08/3
    Basically a Typex Mark 22 machine that was modified electrically and mechanically for the CCM Mark III (BID/08/3A) attachment (see below). The name 'Mark 23' was derived from 'Mark II' and 'variant 3'. This machine is backwards compatible with the Typex Mark 22.

  • CCM Mark III - Combined Cipher Machine
    Typex 23 (i.e. modified Typex Mark 22) with American-built CCM Mark III cipher attachment (BID/08/3A) to convert the machine into a Combined Cipher Machine (CCM), used for wartime and post-war communication with the American CCM/SIGABA.

  • Typex Mark X - Mercury
    Post-war online cipher machine based on the Typex design.

Typex Mark III, portable version of the Mark II Mark III Typex Mark IV, portable version Mark VI Typex Mark VIII, with morse perforator Mark VIII Typex Mark 22 - BID/08/02 (Typex Mark II with plugboards) Mark 22 Typex Mark 22 - BID/08/03 (Typex Mark 22 modified for use with CCM Mark III adapter) Mark 23 CCM/Typex (Typex Mark 23 with CCM Mark III adapter) CCM

 
Typex Mark III
The Typex Mark III can be seen as the portable version of the Typex Mark II. It uses the same cipher wheels and its physical appearance is largely identical to the centre part of the Mark II.
 
The machine is hand-operated, but a motor drive attachment was available as an option. It handles 60 characters per minute and the user has to type with the left hand, whilst the right hand is used to operate the crank on the right.

The crank is not only used for the stepping motion of the cipher wheels, but also engages a small electric generator that delivers the current for the cipher maze. Behind the rotor cage is a small printer with a rotating print head that delivers the output onto a 9.6 mm paper strip.

The image on the right shows a beautiful example of a Typex Mark III that came up for auction at Christie's in December 2014 [13]
  
Typex Mark III. Copyright Christie's 2014 [13]. Reproduced with kind permission.

 
Typex Mark III with wooden storage box Typex Mark III Typex Mark III front size Type Mark III right size Type Mark III left side Keyboard Interior of the Typex Mark 22

 
Typex Mark VI
The Typex Mark VI (Mk.6) was a rather small version of the Typex machine, that is driven by an electromotor and prints directly to a (pre-gummed) 9.6 mm paper strip. It is less deep than the Mark III, but is wider and has the actuator/printer attached to the right side of the cipher unit.
 
The cipher wheels are different from the other models, probably to make the machine smaller. A large 32-contact Strowger connector to the left of the keyboard is used for the connection of the external power supply unit.

The image on the right shows a rare example of the Typex Mark VI that was sold in an auction at Bonhams in London in November 2012 [8]. The machine was in excellent condition and came with several reels of paper tape. Unfortunately, the five cipher wheels were missing.
  
Pictures of Typex Mark VI courtesy Bonhams London [8]

 
Typex Mark VI in front of its storage box. Photo courtesy Bonhams [8] Close-up of the keyboard and the reflector. Photo courtesy Bonhams [8] Typex Mark VI inside its storage box. Photo courtesy Bonhams [8]

 
Typex Mark VIII
The Typex Mark VIII is a little known machine which is sometimes described as a Typex Mark II with a morse perforator fitted [1]. Although it is clearly a family member of the Typex Mark II, it has an somewhat different mechanical layout.

The rotor cage is moved towards the left, to make room for the morse perforator which sits immediately behind the keyboard. Furthermore, the machine is suitable for online use and can be synchronised with the two advance and retard buttons at the front of the keyboard.
  
Right view of Typex Mark VIII [20]

 
Left view of Typex Mark VIII [20] Right view of Typex Mark VIII [20]

 
Typex Mark 22
The Typex Mark 22 is arguably the most well-known Typex variant. During WWII it was used at a large scale by the UK for exchanging messages at the highest level. The machine basically consists of a Typex Mark II with additional plugboards mounted at either side of the keyboard.
 
The leftmost plugboard is used as a configurable reflector and is seated in a 32-contact Strowger U-point socket, allowing it to be swapped for another (pre-wired) unit within seconds. It is similar to reflector D (UKW-D) on the Enigma.

The rightmost plugboard is inserted between the keyboard and the entry disc, at the same place as the plugboard on the Enigma. However, as it uses single wires (compared to wire pairs on the Enigma), it allows more permutations and hence offers better cipher security. Nevertheless, it is backwards compatible with military Enigma-I.
  
Typex Mark 23

The latter was extremely useful, as it allowed the machine to be used as an Enigma analogue. After breaking the Enigma keys at Bletchley Park (UK), large rooms filled with Typex Mark 22 machines were used to decipher and print the vast amount of broken German messages.

Some Mark 22 machines were modified into Mark 23 machines to allow interoperability with the American SIGABA cipher machine. Both variants were used for many years after the war by the countries of the British Commonwealth, and to some extent also by the WU (later: NATO).
 
    The image above is of a Typex 23 which is nearly identical to a Typex Mark 22. It will be replaced by an image of a Mark 22 as and when it becomes available.

Typex Mark 23
The Typex Mark 23 is bascially a Mark 22 that has been modified to allow operation as a Combined Cipher Machine (CCM). The CCM modification consisted of the addition of four mounting posts to hold the CCM basket, and an extra connector to the right of the keyboard. 1
 
The image on the right shows a typical Typex Mark 23 machine, of which one of the CCM mounting posts is visible as a brown rod to the right/rear of the keyboard. Apart from the CCM modification, a Mark 23 is identical to a Mark 22.

The Mark 23 was used during World War II for communication with the Americans who used a modified SIGABA machine to do the same. Mark 23 machines can be used as a standard Typex, as a CCM and as a German Enigma analogue.

The machine featured on this page is of this type.
  
Typex Mark 23

 
  1. This extra Jones connector is not present on all Mark 23 models.

Typex Mark 23 Typex mark 23 with main cover removed

 
Combined Cipher Machine   CCM/Typex
In 1943, the Americans and the British agreed upon a common standard for the secure exchange of cipher messages. The British would convert their Typex machine, and the Americans their SIGABA (a.k.a. ECM, Electronic Cipher machine), in order to achieve a mutual standard. Although the TYPEX machine was known to the Americans, SIGABA was never shown to the British.
 
The common machine was called the Combined Cipher Machine (CCM), but it should be noted that there were two versions of this machine: an American one and a British one. Although the machines were compatible in operation, they were actually very different in appearance.

The image on the right shows the British variant: CCM/Typex, which is in fact a standard Typex machine, with a CCM rotor basket installed. The machine shown here is part of the collection of the NCM. Many thanks to historian David Hamer for supplying these photographs [5].

In order to support the CCM rotor set, the Typex Mark 22 machine had to be modified into a Mark 23. The most visible change is the presence of four vertical mounting posts that were used for mounting the CCM rotor basket to it (1).
  
Typex Mark 23 with CCM Mark III adapter fitted. Copyright NCM (via David Hamer). Reproduced here with kind permission [5].

The new rotor basket (2) was mounted above the normal drum and connected to the Typex via a large plug that was inserted into the socket at the right side of the keyboard (3). The plug that was previously connected to this socket, was inserted into a socket on the CCM basket (4).
 
The image on the right shows the CCM unit for Typex in a wooden transit case, just as it was delivered by the factory. It consists of a sturdy metal base plate, with a 5-rotor drum at the front, similar to the one used in CCM/SIGABA.

The actual cipher wheels are not present in the photograph. They would be inserted in between the contact plates of the drum. Towards the rear is a large switch (5) that was used to select the mode of operation: ENCIPHER or DECIPHER.

The base plate was mounted on top of a Typex and bolted in place by means of four rigged screw terminals at the corners. The entire mechanism is driven by a metal lever (6) at the center that was attached to the cam shaft of the Typex. According to the serial number plate at the front, the unit is called C.C.M. Mark III.
  
CCM Mark III adapter. Copyright NCM (via David Hamer). Reproduced here with kind permission [5].

The CCM Mark III adapter is also known as BID/08/3A (probably named after the BID/08/3). Although there are some similarities, the CCM/Typex rotor basket shown here is different from the one used in the CCM/SIGABA. Furthermore the mounting screws are at different positions. The presence of the ENCYPHER/DECYPHER switch (5) suggests that encryption was not reciproke (i.e. not reversable). On the SIGABA, such a switch was already present at the front right top.
 

The short video clip above shows a complete CCM/Typex, which consists of a Typex Mark 23 and a CCM Mark III adapter, as it was displayed by NSA historian David Hatch at the third bi-annual Crypto Symposium in Charlotte (North Carolina, US) on 25 March 2016. Thanks for bringing it.
 
CCM/SIGABA
As noted before, there are two versions of the CCM: the British CCM/Typex (shown above) and the American CCM/SIGABA, shown below. Both were standard machines that were converted to compatible CCM machines. The modification kits for both versions, were made by the Americans.
 
Whilst the UK's Typex machine was known to the Americans, the Americans never showed the original SIGABA (ECM) to the British. SIGABA was far more complex than Typex and was thought to be cryptographically superior, whilst Typex was merely a copy of the German Enigma.

Whilst the initial CCM/SIGABA machines could be converted back to a standard SIGABA when necessary, later versions were built as dedicated CCM machines in which the SIGABA-specific parts had been omitted or changed.

The image on the right shows an example of a CCM/SIGABA that was later used by NATO.

 More about SIGABA
  
SIGABA CCM CSP-1700

 
Typex machine with supporting posts for CCM modification Close-up of the main shaft of a modified Typex CCM/Typex machine CCM/Typex rotor basket CCM/Typex rotor basket in transit box

 
NATO and CCM
In the years following WWII, the alliance of West-European states, known as the Western Union (WU), used the remaining Typex and CCM machines for communication between the member states. The WU was dissolved into the North Atlantic Treaty Organisation (NATO) in 1949.

In the early years of the NATO, the links between NATO headquarters and the UK mainly consisted of Typex machines, whilst CCM machines were used for communication between the other member states and NATO. The following types of CCM were recognised by NATO [14]:
 
  • CCM Mark III - Typex
    This version is a modified British Typex Mark 23 or BID/08/3 1 with a BID/08/3A CCM adapter. These machines were distributed to the Navies of the NATO member states.

  • CCM Mark II - CSP 1700
    This is the CCM/SIGABA shown above, but unlike the CCM Mark I, which was basically a SIGABA (ECM-Mark II) with an adapter, the CSP-1700 could not be converted back to a SIGABA as the contacts and wiring for the additional wheels had been removed. These machines were distributed to the Navies of the NATO members.

  • CCM Mark II - SIGROD
    This is basically the same machine as the CSP 1700 2 above, albeit with an Army designator (SIGROD) rather than a naval one (CSP 1700). These machines were distributed to the Armies and Air Forces of the NATO member states.
Although all CCM types were used by NATO until at least 1955, it was known by US and British cryptanalists as early as 1948 that the security of the CCM was rapidly declining [15]. Several improvements were suggested, such as the addition of conditional reverse wheel stepping and the development of a BRUTUS rotor basket [16], but eventually the events were overtaken by the adoption of the AFSAM-7 (later: KL-7 or TSEC/KL-7) by NATO and its member states.
 
  1. The original document [14] identifies the CCM/Typex as BID/08/8, but we believe this to be a typo. The Typex variant that was modified for use with the BID/08/3A adapter, was designated BID/08/3.
  2. In some literature, it is suggested that SIGROD was a different machine that was considered as a possible replacement for the SIGABA ECM-II [17]. However, we have found no evidence to support this claim and the NATO designation CCM Mark II clearly confirms that it is basically the same machine as the CSP 1700.


Typex as Enigma
During WWII, the codebreakers at Bletchley Park (BP) had to break the Enigma keys of a wide variety of German radio networks. This involved the use of a large number of electromechanical codebreaking machines, known as Bombes, some of which were located outside of BP for safety.
 
Once the keys had been recovered however, a vast quantity of intercepted messages had to be deciphered, which was a time consuming task. At the height of the war this could amount to thousands of messages on a single day. Ideally original military Enigma machines would be used for this, but given the fact that only a handful had been captured, this was not realistic.

As Typex is a close relative of Enigma (after all the original Typex design was based on the commercial Enigma), it was possible to convert a Typex machine into an 'Enigma Simulator'.

Typex room at Bletchley Park. Crown Copyright.

For this, the Typex Mark 22 was used, as it had already been upgraded to include a plugboard and a pluggable reflector. By making new - Enigma compatible - cipher wheels and wiring cores, and configuring the two plugboards appropriately, Typex could be used as an Enigma Double. The image above shows a Typex room with approx. 25 machines at Bletchley Park during the war.
 
Differences with Enigma
Although Typex was clearly based on the design of the German Enigma machine, it has a number of advantages, including the ones listed here:
 
  • More cipher wheels
    Typex features 5 cipher wheels, whereas Enigma has only 3 cipher wheels (or 4 in case of the Enigma M4). Note however, that the first two wheels are static, which means that they can be set to a given position, but do not move during enciphering. This is similar to the effect of the extra (4th) wheel of the Enigma M4.

  • Multiple turnover notches
    The cipher wheels of Typex have more than one turnover notch (typically 5, 7 or 9) whereas most Enigma wheels have only one turnover notch. The extra notches cause a more frequent (and therefore less predictable) wheel stepping motion. Multiple turnover notches were also featured on the Enigma G and Enigma T models.

  • Non-reciproke plugboard
    Typex 22 (i.e. modified Typex Mark II) has a single-ended plugboard, allowing each letter to be mapped to any other letter of the alphabet, whereas Enigma's plugboard always swaps letters in pairs (e.g. if A becomes G, then G becomes A). This makes the Typex plugboard cryptographically stronger.

  • Single operator
    Typex can be operated by a single person, whilst at least two people were generally needed for Enigma: one to type the letters and one to write down the resulting ciphertext.

  • Built-in printer
    Typex prints its output directly onto a paper strip, whereas Enigma delivers its output by means of a lamp panel. This makes Typex not only faster, but also avoids making mistakes by misreading letters from the lamp panel.

  • Link to teleprinter
    Typex Mark I had to be attached to a teleprinter, whilst Typex Mark II could be attached to a teleprinter if necessary. This allowed messages to be sent directly in baudot code, avoiding the time consuming process of converting and sending messages in morse code.

Cryptanalysis of Typex
For information about cryptanalysis of Typex, see [18] and [19].
 



Type Mark 23 interior with the keyboard removed

 
Interior
Typex II, mark 22 and Mark 23 consists of a large die-cast chassis with a number of functional building blocks. The chassis itself consists of the main machine chassis at the center and two for the printer assemblies bolted to the sides of the main chassis. Most of the building blocks, such as the keyboard, the printers and the actuator, can be removed easily in just a few minutes.
 
Keyboard
In principle, Typex is only capable of encoding the 26 letters of the Latin alphabet (A-Z), just like the German Enigma machine. But as the printers are capable of printing letters, numbers and punctuation marks, a clever trick is used to shift between letters and figures and to insert spaces.
 
For this, the least used keys are converted into MODE-selectors. The letter Z is used to switch to figures mode, whilst the V returns the machine to letters. The letter X is used to insert a space.

The shifted characters (figures) are shown in red on the key tops. In case the letters Z, V and X are needed, they should be treated as figures. This means that the letter X needs three key strokes: one to switch to figures, one to print the X (i.e. the GX-key), and one to return to letters. The same is true for the letter V which sits above the C, and the letter Z which sits above the D.
  
Typex keyboard

The image above shows the keyboard after it has been removed from the machine. It is a complete stand-alone unit that can be removed after loosening four large bolts in the bottom frame. The spacebar is mechanically linked to the X-key. Pressing SPACE will engage the X-key.
 
In the same way the FIGs key is linked to the Z and the LETTs key to the V. The bracket at the far right is for mounting a character counter. It is incremented by the main wheel stepping lever.

Below the keyboard a a set of 26 single-pole double-throw (SPDT) switches, divided over three rows. Each key on the keyboard engages one switch. The purpose and operation of these switches is identical to the keyboard switches of the Enigma cipher machine. The normally-open contact is connected to the battery, whilst the common contact is connected to the entry disc.
  
Keyboard contacts

The normally-closed contact is connected directly to the one of the solenoids of the printer, which takes the place of the lamps on the Enigma lamp panel. When the user presses a key, the corresponding contact sends a current into the cipher maze (i.e. the wired wheels) and the returning current will activate one of the printer solenoids and cause a character to be printed.
 
Typex keyboard Keyboard front view Keyboard close-up Keyboard lockout mechanism Keyboard bottom view Keyboard contacts Close-up of keyboard contacts

 
Stepping unit
The core of the Typex cipher machine is the rotor basket or wheel cage or stepping unit, which is located just behind the keyboard. In normal use it is hidden from view by the copy holder and the top lid of the case. This part is also known as the cipher maze or wiring maze of the machine.
 
The stepping unit is very similar to the one in the German Enigma machine, except that two extra (non-moving) wheels have been added to the right of the three moving ones. At the far right is the entry disc. The reflector is located at the left.

At the top are five red rollers that will lock the wheels into the current position. Just below these rollers are the actual stepping arms. Like on Enigma, the leftmost three stepping arms can be adjusted through holes in the bottom of the machine. The stepping arms of the rightmost 2 wheels are disabled by means of a metal strip.
  
Drum

Like the cipher wheels, both the entry disc and the reflector have a double row of contacts. Although it is sometimes thought that this is part of the cipher, they are actually connected in parallel and are only present to ensure a proper and more reliable contact between the wheels.
 
Drum Entry disc Reflector Wheel stepping levers Wheel locking rollers Stepping lever Adjustment screws for the leftmost three stepping arms

 
Actuator
The entire operation of the machine is controlled by a mechanical sub-system that is mounted behind the rotor cage. It is known as the cam unit or actuator and ensures that all parts of the machine are synchronised. Central to the actuator is a cam shaft that runs from left to right.
 
The actuator is driven from the rear by a motor and is operated by five electromagnets that are activated by the keyboard. A large lever on the cam shaft is fitted to a metal bar that controls the stepping motion of the cipher wheels.

The unit has two seesaw levers at either side that operate the printers. The frontmost seesaw lever is used to toggle between letters and figures, whilst the one at the rear controls the printer stepping. The actuator is connected to the electrical system of the machine via a 10-contact Stowger U-point connector at the rear.
  
Actuator front view

The actuator sub-system is a complete self-contained stand-alone unit. Once the printers have been removed from the chassis, the actuator can be removed in less than a minute, simply by loosening four large bolts at the bottom and lifting the unit from the Strowger socket at the rear.
 
Actuator front view Actuator rear view Actuator top view Two seesaw levers at the side of the actuator (cam unit) Stepping actuator on main shaft Stepping lever attached to actuator Actuator unit connected to main chassis

 
Printer
Typex Mark II, Mark 22 and Mark 23 each have two printers that are visible as large bulky black cylinders at either side of the machine. Although these printers seem to be somewhat oversized for the machine, they are actually capable of printing text at a speed of 300 characters/minute.
 
The printer basically consists of two parts: a paper and ink ribbon mechanism at the bottom, and a hinged unit with 26 type-arms and 26 solenoids at the top. The hinged top section can be tilted in order to get access to the ink ribbon and the paper feed below. The image on the right shows the printer with tilted top section.

The leftmost printer is used for printing plain­text, whereas the one on the right is used for ciphertext. The mechanical motion of the printer is controlled by a seesaw lever at the side, which is atcuated by the actuator or cam unit. Another seesaw lever, which is also actuated by the cam unit, is used to toggle between letters and figures. The seesaw levers are present at both sides of the mechanism, so that each printer can be mounted at either side of the cam unit.

A narrow 9.6 mm paper strip is fed into the printer from the rear and leaves it at the front, so that the text is immediately available to the operator. Both plain and pre-gummed paper strips were used for this. The paper is advanced by the motion of the rearmost seesaw lever, each time the user presses a key on the keyboard.
  

At the same time, the ink ribbon is moved to the next position. An automatic reverse mechanism ensures that the ink ribbon is reversed when it reaches the end. The printer accepts standard Creed ink ribbons which were commonly used on the Creed teletypewriters of the era.
 
In order to reach the impressive typing speed of 300 characters per minute, the Typex printers use a system of type bars that are arranged in a circle. At the end of each arm is a head with two mirrored characters on its surface. The arms are hinged in such a way that the type heads strike the ribbon and paper in the centre of the circle.

The picture on the right shows a close-up of some of the type heads. Each head accomodates two characters: a letter and a figure (a number, a punctuation mark or a letter) that are positioned in such a way that by default the letter is printed.
  
Close-up of some type arms

Under control of the cam unit, the frontmost seesaw lever is used to toggle between letters and figures. When figures mode is selected, the entire assembly in the lower section of the printer moves slightly forward, so that the alternative character on each type head is now at the center.
 
26 solenoids are mounted at the circumference of the printer. Each solenoid directly controls the movement of a single type arm. The solenoids are connected to the normally closed contact of the keyboard switches and take the place of the lamps on the Enigma lamp panel. When the user presses a key and the current is returned by the cipher maze (drum), the corresponding solenoid is actuated, which in turn moves its type arm.

The image on the right shows one of the type arms half way down on its way to strike the ink ribbon and the paper a few centimeters below.
  
Activated type arm

The solenoids are electrically wired to the keyboard switches via the large 32-contact Strowger U-point connector at the rear. The printer can be removed from the chassis in less than a minute, simply by releasing three bolts in the bottom panel and lifting the unit from the Strowger socket.
 
Printer seen from the front Printer seen from the rear Looking into the printer from the top Activated type arm Top section half-tilted Close-up of the lower section Seesaw levers at both sides Electrical connections at the rear

 
Documentation
  1. Maintenance of Typex Machine Marks IA, IB, II, III and VI by code and cipher personnel
    Air Ministry. Date unknown. 74 pages. 1

  2. TYPE X Machine, Mk. VI
    Air Ministry. January 1943. 21 pages.

  1. Document kindly provided by John Harper.

References
  1. Wikipedia, Typex
    Retrieved April 2012.

  2. Kevin Coleman, Volunteer at Bletchley Park
    Some photographs on this page courtesy Kevin Coleman. September 2009.

  3. Jerry Proc and contributors, TYPEX
    History/development of Typex by various contributors.

  4. James Rusbridger and Eric Nave, Betrayal at Pearl Harbor
    ISBN 1-85479-162-1. Cornwall (UK) 1992. pp. 226-232.

  5. National Cryptologic Museum, Photographs of CCM/Typex
    Supplied by David Hamer and reproduced here with kind permission.
    Retrieved November 2012.

  6. Wikipedia, Combined Cipher Machine
    Retrieved November 2012.

  7. Jerry Proc's crypto pages, CCM Mk II (Combined Cipher Machine)
    Retrieved November 2012.

  8. Bonhams (London), Auction of Typex Mark VI (S/N: 6077)
    Images of Typex Mark VI reproduced here with kind permission.
    19799, lot 79, 14 November 2012, sold for GBP 13,750.

  9. Typex Maintenance Manual
    Date unknown.

  10. Wikipedia, Powers-Samas
    Retrieved May 2015.

  11. Ralph Erskine, The Development of Typex
    The Enigma Bulletin, No. 2, May 1997. pp. 69-86.

  12. Ralph Erskine, The Admiralty and Cipher Machines During the Second World War: Not So Stupid After All
    The Journal of Intelligence History 2, (2) 2002. pp. 49-68.

  13. Christie's, A British Typex Cipher Machine
    Online Auction - Code Breakers, Enigmas and other Cipher Machines - Lot 4
    19 November 2014 to 3 December 2014. Retrieved May 2015.
    Photographs reproduced here with kind permission.

  14. NATO, CCM Systems for NATO
    SGM-1922-51. 10 November 1951. NATO SECRET.
    Declassified by NATO on 12 October 1994 (IMSM-431-99).

  15. US Navy, Comments on Army Proposals Regarding the CCM
    10 January 1948. SECRET.
    Declassified by NSA on 20 September 2013 (EO 13526).

  16. Richard James Aldrich, Espionage, Security and Intelligence in Britain, 1945-1970
    ISBN 0-7190-4955-5 (hardback) 0-7190-4956-3 (paperback). 1998. pp. 51-53.

  17. John Savard and Richard Pekelney,The ECM Mark II: Design, History and Cryptology
    Cryptologia, Vol. 23(3), July 1999, pp. 211-228.

  18. Kelly Chang, Cryptanalysis of Typex
    Master's Projects. paper 235. May 2012.

  19. Kelly Chang, Richard M. Low & Mark Stamp, Cryptanalysis of Typex
    Cryptologia, Volume 38, Issue 2, April 2014. pp. 116-132.

  20. Anonymous contributor, Images of Typex Mark VIII
    August 2015.

Further information

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Crypto Museum. Created: Wednesday 12 August 2009. Last changed: Friday, 01 July 2016 - 23:33 CET.
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