Editing Typex (section)

==History and development==
By the 1920s, the British Government was seeking a replacement for its [[book cipher]] systems, which had been shown to be insecure and which proved to be slow and awkward to use. In 1926, an inter-departmental committee was formed to consider whether they could be replaced with cipher machines. Over a period of several years and at large expense, the committee investigated a number of options but no proposal was decided upon. One suggestion was put forward by Wing Commander [[Oswyn G. W. G. Lywood]] to adapt the commercial Enigma by adding a printing unit but the committee decided against pursuing Lywood's proposal.

[[Image:Typex-Mk-III.jpg|thumb|Typex Mk III was a portable version powered by a handle.]]

In August 1934, Lywood began work on a machine authorised by the [[Royal Air Force|RAF]]. Lywood worked with J. C. Coulson, Albert P. Lemmon, and Ernest W. Smith at [[Kidbrooke]] in [[Greenwich]], with the printing unit provided by [[Creed & Company]]. The first prototype was delivered to the [[Air Ministry]] on 30 April 1935. In early 1937, around 30 Typex Mark I machines were supplied to the RAF. The machine was initially termed the "RAF Enigma with Type X attachments".

The design of its successor had begun by February 1937. In June 1938, '''Typex Mark II''' was demonstrated to the cipher-machine committee, who approved an order of 350 machines. The Mark II model was bulky, incorporating two printers: one for plaintext and one for ciphertext. As a result, it was significantly larger than the Enigma, weighing around {{cvt|120|lb|kg}} , and measuring {{cvt|30|in|mm}} × {{cvt|22|in|mm}} × {{cvt|14|in|mm}}. After trials, the machine was adopted by the RAF, Army and other government departments. During [[World War II]], a large number of Typex machines were manufactured by the tabulating machine manufacturer [[Powers-Samas]].<ref>Campbell-Kelly</ref><!--this is a "vicarious" citation. This info is attributed to this source by John Keen in his book on the Bombe.-->

'''Typex Mark III''' was a more portable variant, using the same drums as the Mark II machines powered by turning a handle (it was also possible to attach a motor drive). The maximum operating speed is around 60 letters a minute, significantly slower than the 300 achievable with the Mark II.

'''Typex Mark VI''' was another handle-operated variant, measuring {{cvt|20|in|mm}} ×{{cvt|12|in|mm}} ×{{cvt|9|in|mm}}, weighing {{cvt|30|lb|kg}} and consisting of over 700 components.

Plugboards for the reflector were added to the machine from November 1941.

For inter-Allied communications during [[World War II]], the [[Combined Cipher Machine]] (CCM) was developed, used in the [[Royal Navy]] from November 1943. The CCM was implemented by making modifications to Typex and the United States [[ECM Mark II]] machine so that they would be compatible.

'''Typex Mark VIII''' was a Mark II fitted with a morse perforator.

'''Typex 22''' (BID/08/2) and '''Typex 23''' (BID/08/3) were late models, that incorporated plugboards for improved security. Mark 23 was a Mark 22 modified for use with the CCM. In [[New Zealand]], Typex Mark II and Mark III were superseded by Mark 22 and Mark 23 on 1 January 1950. The Royal Air Force used a combination of the Creed Teleprinter and Typex until 1960. This amalgamation allowed a single operator to use punch tape and printouts for both sending and receiving encrypted material.

Erskine (2002) estimates that around 12,000 Typex machines were built by the end of World War II.