Baudot, refined into ITA2, is a 5-bit character encoding from the era of telegraph and telex machines. Five bits give only 32 possible codes, far fewer than the characters needed, which is solved with mode shifting.

What are LTRS and FIGS?

Because 32 codes cannot cover letters, digits and punctuation, ITA2 uses two modes. LTRS (11111) switches to letters and FIGS (11011) switches to figures and punctuation. The encoder inserts these markers automatically when the mode must change.

Why are some characters dropped?

ITA2 has a very small repertoire. Lowercase is folded to uppercase, and any character with no ITA2 representation, such as most modern symbols, is reported as skipped rather than encoded incorrectly.

Why do space and newline not trigger a shift?

Space, carriage return and line feed occupy the same code in both the letters and figures modes. The encoder can emit them without inserting a shift marker, which keeps the output compact.

Is ITA2 the same as the original Baudot code?

Not exactly. Émile Baudot's original 5-bit code was reorganised by Donald Murray and then standardised as the International Telegraph Alphabet No. 2. ITA2 is the version this tool implements and the one used by most telex networks.

Baudot / ITA2 Encoder

Long before ASCII, teleprinters spoke in five bits. This encoder turns ordinary text into ITA2 Baudot codes, handling the letters-versus-figures shifting that made a 32-code alphabet cover far more than 32 characters.

How it works

ITA2 assigns each printable character a 5-bit code. With only 32 codes available, the same bit pattern means two different things depending on the current mode. Two reserved codes switch modes:

LTRS = 11111  (switch to letters)
FIGS = 11011  (switch to figures and punctuation)

The encoder tracks the current mode. When the next character lives in the other mode, it first emits the appropriate shift marker, then the character’s code. Space, carriage return and line feed share one code across both modes, so they never force a shift.

Tips and notes

Lowercase input is folded to uppercase, since ITA2 has no lowercase.
The shift markers add to the code count whenever you alternate between letters and digits, which is why mixed text expands more than its character count.
Characters outside the ITA2 repertoire are listed as skipped rather than silently mis-encoded.