Editing Typex (section)

==Description==
Like Enigma, Typex was a [[rotor machine]]. Typex came in a number of variations, but all contained five rotors, as opposed to three or four in the Enigma. Like the Enigma, the signal was sent through the rotors twice, using a "[[Reflector (cipher machine)|reflector]]" at the end of the rotor stack. On a Typex rotor, each electrical contact was doubled to improve reliability.

Of the five rotors, typically the first two were stationary. These provided additional enciphering without adding complexity to the rotor turning mechanisms. Their purpose was similar to the plugboard in the Enigmas, offering additional randomization that could be easily changed. Unlike Enigma's plugboard, however, the wiring of those two rotors could not be easily changed day-to-day. Plugboards were added to later versions of Typex.

The major improvement the Typex had over the standard Enigma was that the rotors in the machine contained multiple notches that would turn the neighbouring rotor. This eliminated an entire class of attacks on the system, whereas Enigma's fixed notches resulted in certain patterns appearing in the cyphertext that could be seen under certain circumstances.

[[Image:Typex nocase.jpg|right|thumbnail|upright=1.2|The Typex 23, pictured, was similar to the Mark 22, but modified for use with the Combined Cypher Machine (CCM).]]

Some Typex rotors came in two parts, where a ''slug'' containing the wiring was inserted into a metal casing. Different casings contained different numbers of notches around the rim, such as 5, 7 or 9 notches. Each slug could be inserted into a casing in two different ways by turning it over. In use, all the rotors of the machine would use casings with the same number of notches. Normally five slugs were chosen from a set of ten.

On some models, operators could achieve a speed of 20 words a minute, and the output ciphertext or plaintext was printed on paper tape. For some portable versions, such as the Mark III, a message was typed with the left hand while the right hand turned a handle.<ref>Deavours and Kruh</ref>

Several Internet Typex articles say that only [[Vaseline]] was used to lubricate Typex machines and that no other lubricant was used. Vaseline was used to lubricate the rotor disc contacts. Without this there was a risk of arcing which would burn the insulation between the contacts.  For the rest of the machine two grades of oil (Spindle Oils 1 and 2) were used. Regular cleaning and maintenance was essential. 
In particular, the letters/figures cam-cluster [[Balata (latex)|balata]] discs had to be kept lubricated.{{citation needed|date=December 2012}}