Editing Baudot code (section)

==Details==
{{More citations needed section|date=November 2023}}
Note: This table presumes the space called "1" by Baudot and Murray is rightmost, and least significant. The way the transmitted bits were packed into larger codes varied by manufacturer. The most common solution allocates the bits from the least significant bit towards the most significant bit (leaving the three most significant bits of a byte unused).
[[File:Ita2.png|right|frame|Table of ITA2 codes (expressed as [[hexadecimal]] numbers)]]
In ITA2, characters are expressed using five bits. ITA2 uses two code sub-sets, the "letter shift" (LTRS), and the "figure shift" (FIGS). The FIGS character (11011) signals that the following characters are to be interpreted as being in the FIGS set, until this is reset by the LTRS (11111) character.<ref>{{FOLDOC|Baudot+code}}</ref> In use, the LTRS or FIGS shift key is pressed and released, transmitting the corresponding shift character to the other machine. The desired letters or figures characters are then typed. Unlike a typewriter or modern computer keyboard, the shift key isn't kept depressed whilst the corresponding characters are typed. "ENQuiry" will trigger the other machine's answerback. It means "Who are you?"

CR is [[carriage return]], LF is [[line feed]], BEL is the [[bell character]] which rang a small [[bell (instrument)|bell]] (often used to alert operators to an incoming message), SP is space, and NUL is the [[null character]] (blank tape).

Note: the binary conversions of the codepoints are often shown in reverse order, depending on (presumably) from which side one views the paper tape. Note further that the [[control character|"control" characters]] were chosen so that they were either symmetric or in useful pairs so that inserting a tape "upside down" did not result in problems for the equipment and the resulting printout could be deciphered.  Thus FIGS (11011), LTRS (11111) and space (00100) are invariant, while CR (00010) and LF (01000), generally used as a pair, are treated the same regardless of order by page printers.<ref>{{cite web|url=https://www.sr-ix.com/Archive/CharCodeHist/index.html#ITA2|title=An annotated history of some character codes: ITA2|last=Jennings|first=Tom|author-link=Tom Jennings|date=5 February 2020|access-date=1 June 2022|quote=[...] the characters that are 'transmission control' related [...] are bit-wise symmetrical – the codes for FIGS, LTRS, space and BLANK – are the same reversed left to right! Further, the codes for CR and LF, equal each other when reversed left to right!}}</ref> LTRS could also be used to overpunch characters to be deleted on a paper tape (much like DEL in 7-bit [[ASCII]]).

The sequence ''[[RY (test signal)|RYRYRY...]]'' is often used in test messages, and at the start of every transmission. Since R is 01010 and Y is 10101, the sequence exercises much of a teleprinter's mechanical components at maximum stress.  Also, at one time, fine-tuning of the receiver was done using two coloured lights (one for each tone).  'RYRYRY...' produced 0101010101..., which made the lights glow with equal brightness when the tuning was correct. This tuning sequence is only useful when ITA2 is used with two-tone [[Frequency-shift keying|FSK]] modulation, such as is commonly seen in [[radioteletype]] (RTTY) usage.

US implementations of Baudot code may differ in the addition of a few characters, such as #, & on the FIGS layer.

The Russian version of Baudot code ([[MTK-2]]) used three shift modes; the [[Cyrillic letter]] mode was activated by the character (00000). Because of the larger number of characters in the Cyrillic alphabet, the characters [[Exclamation Mark|!]], [[Ampersand|&]], [[Pound sign|£]] were omitted and replaced by Cyrillics, and [[Bell character|BEL]] has the same code as Cyrillic letter Ю. The Cyrillic letters [[Ъ]] and [[Yo (Cyrillic)|Ё]] are omitted, and Ч is merged with the numeral 4.