Baudot / ITA2 Code Decoder

Encode and decode text using 5-bit ITA2 teletype code. Visualize as punched paper tape.

Plain Text
ITA2 Bit Codes (5-bit groups)
Enter text to encode to Baudot ITA2.

How to Use the Baudot Decoder

  1. Encode — type plain text. The tool outputs 5-bit ITA2 code groups, including Letters/Figures shift codes where needed.
  2. Decode — paste 5-bit groups (space-separated) to recover the original text.
  3. Tape View — type text and see it rendered as a punched paper tape diagram with holes representing 1-bits.
  4. Reference — full ITA2 character table with binary codes, decimal values, and both Letters and Figures interpretations.

About Baudot and ITA2

Baudot code was invented by French telegraph engineer Émile Baudot in 1870 and patented in 1888. It was the first character encoding to use a fixed-length binary scheme — every character encoded in exactly 5 bits, producing 32 possible codes. This was a major advance over Morse code, which uses variable-length sequences of dots and dashes and requires a skilled human operator to send and receive at speed. Baudot's encoding allowed a relatively unskilled operator to type text on a piano-style keyboard while an automatic mechanism handled the electrical transmission.

The ITU standardized an improved version as ITA2 (International Telegraph Alphabet No. 2) in 1932. ITA2 remained the standard for international telex systems for most of the 20th century and is still in use in TTY/TDD devices for deaf communication, amateur radio RTTY, and some legacy maritime communication systems.

The Letters/Figures Shift System

With only 32 code points, ITA2 cannot represent all letters and figures simultaneously. Instead, it uses two shift states. In Letters mode (the default), codes map to uppercase letters A-Z and a few control characters. In Figures mode, the same codes map to digits 0-9 and punctuation marks. Two special codes — Letters Shift (11111, decimal 31) and Figures Shift (11011, decimal 27) — switch between modes. A receiver must track the current shift state to interpret each incoming character correctly.

Paper Tape Format

ITA2 messages were traditionally stored and transmitted on punched paper tape. The tape has five data channels (representing the five bits) arranged across its width, plus a smaller sprocket hole column used for driving the tape mechanism. A punched hole represents a 1 bit; an unpunched position is 0. Reading the tape one row at a time from left to right gives the sequence of characters. The narrow, low-tech paper tape was robust and archival — many original teletype tapes from the mid-20th century survive in archives today.

Legacy and Modern Use

ITA2 was largely replaced by ASCII in computer systems from the 1960s onward. ASCII uses 7 bits and eliminates the need for shift states by providing separate codes for both letters and figures. However, ITA2 survives in TTY/TDD telecommunications devices mandated by accessibility law in many countries, in amateur radio Radioteletype (RTTY) transmissions, and in some older naval and maritime signaling systems. Explore our Dancing Men Cipher and Scytale Cipher for more historical encoding tools.

Frequently Asked Questions

Baudot code is a 5-bit character encoding invented by Émile Baudot in 1870 for telegraph and teletype machines. Each character is represented by 5 binary bits. ITA2 is the international standardized version, still used in some TTY and telex systems.
Since 5 bits only allows 32 codes, Baudot uses two shift states. Letters mode maps codes to uppercase letters. Figures mode maps the same codes to numbers and punctuation. Special codes switch between modes, similar to Shift Lock on a keyboard.
ITA2 (International Telegraph Alphabet No. 2) is the international standardization of Baudot code adopted by the CCITT in 1932. It defines specific bit patterns for each character and is the basis for most teletype and telex communications that followed.
Baudot paper tape has 5 data channels plus a sprocket hole. A punched hole is a 1 bit; unpunched is 0. Each row of 5 holes encodes one character. You read tape row by row to decode the message.
Yes. ITA2 Baudot code is still used in TTY/TDD devices for the deaf and hard-of-hearing, amateur radio RTTY (Radio Teletype), and some legacy telex networks. Modern systems mostly use ASCII or Unicode, but ITA2 remains active in niche contexts.