What was Typex?

Typex - the history of the cipher machine

Typex was a rotor-based British cipher machine adapted from the commercial Enigma but with a few changes to make the cipher more secure. It was developed by Wing Commander Oswyn G.W. Lywood together with Flight Lieutenant Coulson, Mr. E. W. Smith and Sergeant Albert Lemon at the RAF's wireless establishment at Kidbrooke, southeast London.

The machine has a total of five rotors of which the left-hand three rotate as per Enigma while the two right-hand ones can be set at the start of encryption but stay static and do not rotate. The rotors themselves are again similar in function and look to Enigma but generally with more notches than the standard Enigma's rotors giving a higher security level.

Typex models

Over its lifetime, several different models of Typex were created, starting with the first prototype in 1934/35.

RAF Enigma with Type-X Attachments

The initial prototype was a cumbersome machine which basically consisted of a standard Creed teletype with an Enigma rotor basket grafted on the front. The entire machine weighed over 120 pounds (54.4 kg) and needed a 230-volt AC power supply, rather than Enigma's battery system. The main benefit though was the included printers which printed the plain and cipher texts rather than requiring a second operator to record the glow lamps which Enigma required.

The new prototype was demonstrated to the Cipher Committee in 1937 but they were unimpressed and refused to authorise further development. Undeterred, the RAF decided to continue anyway and approached the Creed & Company in Croyden, London to build the first production models.¹

Typex Mark I

An initial design and production of a further twenty-nine machines, based on the original prototype, were built by Creed & Company, the Enigma part of the name having been dropped. These were used to equip the main RAF headquarters in early 1937. (I have so far been unable to find any images of the Typex Mark I - let me know if you have seen one!)

Typex Mark II

The much improved Typex Mark II was produced by 28th May 1937 and was by far the most widely used Typex model. It included two printers which could handle an impressive 300 characters per minute but it was not portable like Enigma, weighing around 120 lb (54 kg) and measuring 30 in (760 mm) × 22 in (560 mm) × 14 in (360 mm). This model did not include a wireable plugboard like the military Enigma (this was an unknown addition at this time), although the two extra static rotors gave much the same effect.

It was shown to the Cipher Committee on 14th June and an order for 350 Mark II machines for the RAF was approved at the cost of £107.8.0 each. The Navy initially ordered five for Naval trials which were received by late summer, 1939 which were in operation in Admiralty and at Malta and Gibraltar by the end of the year.

To give the idea of the numbers of machines manufactured, we can find some information² from Navy records. "The tests proved successful, and in May 1939, a further 50 machines were ordered for Naval use. After the outbreak of the War, another 575 machines were ordered for the Navy.", "Further orders for machines to meet Naval requirements were placed at intervals throughout the war up to a total of 3,302. Of this number, some 2,300 had been delivered by the end of hostilities."

Typex Mark III

The Typex Mark III is very much like a smaller, hand-operated version of the Mark II. It uses the same cipher wheels and almost identical rotor basket. It has just one printer which outputs either the cipher text or plain text onto paper tape dependant on the position of the cypher/decypher lever.

The message is typed with the left-hand with the right turning the handle which rotates the rotors and activates the printer mechanism. There is no external mains or battery required for this machine as the handle rotation gives enough mechanical and electric power via a small electric generator. The printer uses a rotating print head, continuously inked, which has the paper pulled onto the head at the correct point to print the required character.

Typex Mark III, converted to use lampboard

This unique modification to a standard Typex Mark III, which is at the Communications and Electronic Museum in Kingston, Ontario, replaces the printer with a lampboard! The information below is from Jerry Proc's crypto website

"On the surface, it appears that a lampboard has been married to a MK III Typex keyboard with a slightly modified rotor basket, however there is no evidence of the crank normally found on the right side of the machine. Since this variant needs power for the lamp board and the Mk III doesn't, one can only speculate if the entire machine uses power thus eliminating the crank for the internal power generator.
This variant may have been created for the purposes of training operators or maintainers in order to illustrate the principle of the Typex since the machine was actually modelled on the German Enigma. Another theory suggests this variant was used at Camp-X near Oshawa , Ontario in an operational capacity."

Typex Mark IV

Typex Mk IV was built around the Creed Model #7 teletype and printed out the text on rolls of message forms.

Typex Mark V

There is not much information available on this model. Possibly an experimental, or limited production run model.

Typex Mark VI

Typex Mark VI (Mk 6) was another portable model which used a different size of cipher wheels (possibly to make the machine smaller). It weighed around 30 pounds (13.6Kg) and measured 20 x 12 x 9 inches.

It used a different arrangement from the other machines, the keyboard and drum unit being on the left with two printers mounted on the right printing onto the same pre-gummed, 9.6mm paper strip.

Typex Mark VII

There is not much information available on this model. Possibly an experimental, or limited production run model.

Typex Mark VIII

Typex Mk VIII was the first model capable of interfacing with other Typex machines sending and receiving Morse code transmissions and automatically converting them into printed plain text.

The rotor cage is on the left to make room for the Morse perforator which sits behind the keyboard on the right.

Typex Mark 22

The Mark 22 was basically the Mark II with the addition of two plugboards for increased security and it is this model that is simulated on this website. The name derives from Mark II and variant 2, therefore (I believe), pronounced Mark Two-Two rather than Twenty-two.

The plugboards for these models are listed as being added around November 1941, but were not bought into force until around March 1942, when sufficient machines with this capability were available.

The left-hand plugboard is a rewireable reflector while the right works in a similar way to the Enigma's plugboard but does not require the wiring to be reciprocal. Enigma's plugboard cables required letters to be swapped (A to D and also D to A), whereas the Typex version allowed any letter to swap with any other, increasing the number of possible changes, while still retaining the compatibility with Enigma's variant.

This compatibility meant that the Mark 22 was very useful as an Enigma analog and was used at Bletchley Park for deciphering Enigma message after the day key had been recovered on the Bombe machines. With the potential for thousands of messages a day, having a quicker method to decipher the text, rather than manually using the few captured military Enigma machines, was necessary.

Typex Mark 23 (with CCM, Combined Cipher Machine)

In 1943, the British and Americans required a method to communicate cipher messages. The Americans had seen the Typex Mark II but had not released the details of their own cipher machine, the SIGABA. A set of conversion kits were produced for each machine to allow a common standard cipher between the machines. The overall converted Typex / SIGABA system was known as the CCM or Combined Cipher Machine, while the new Typex with CCM adaptor fitted was known as the Typex Mark 23.

For the Typex, an adaptor kit was released to allow an upgrade to the standard Typex Mark 22. The kit included the CCM adaptor itself, a kit of tools & spares, four pillars, a front & rear plug & socket, an extra 30-ohm resistor and various junction blocks, wiring & brackets. This kit could be fitted by engineers on site, but required a number of holes to be drilled and the wiring to be spliced in. A new socket was fitted at the front right by the keyboard plus another with a cable attached at the rear.

Fitting the CCM adaptor required it to be screwed down onto the mounting pillars and connecting the feed pawl lever. The connector from the CCM would be plugged into the socket behind the printer while the plug that was inserted there was connected back to the socket on the side of the CCM. Likewise, a plug and socket from the keyboard would also require swapping over. This made it relatively easy to swap between CCM and Typex modes.

For more details on how the CCM and SIGABA worked, see the information on the cryptomuseum.com website.

Typex in use

Below are a selection of the few available photos showing Typex being used during World War 2 at Bletchley Park. Typex was used, due to it's compatibility with Enigma, to decipher German messages.

The following are photos of the Typex machine being used elsewhere in the world during the war.