Baudot Code (ITA2)

What is Baudot Code?

Baudot code (officially ITA2 - International Telegraph Alphabet No. 2) is a 5-bit character encoding used in teleprinters and early data communications. Named after Émile Baudot, who invented an earlier version in 1870.

How Baudot Works

5-Bit Encoding

Each character is represented by 5 bits, allowing 32 possible combinations (2^5 = 32). Since this isn't enough for letters, numbers, and punctuation, Baudot uses shift characters.

Shift Modes

• Letters Shift (11111): Following codes are letters A-Z
• Figures Shift (11011): Following codes are numbers/symbols

The same 5-bit code can represent different characters depending on the current shift mode.

Baudot in Geocaching

This encoding appears in puzzles because:

• Historical: Telegraph and teleprinter themes
• Binary patterns: 5-bit codes make interesting visual puzzles
• Shift mechanism: Adds complexity to decoding
• Technical: Appeals to tech-themed caches

Recognizing Baudot

Look for these clues:

• 5-bit groups: Binary in groups of 5
• Telegraph references: Mentions of teleprinters, TTY
• Shift codes: 11111 and 11011 appearing in the message
• Limited character set: Only uppercase letters

History

Baudot code was the dominant character encoding for teleprinters from the 1920s through the 1970s. The "baud" unit of data transmission speed is named after Émile Baudot. It was eventually replaced by ASCII and other 7/8-bit encodings.

Related Encodings

• Morse Code: Earlier telegraph encoding.
• ASCII: 7-bit successor to Baudot.
• EBCDIC: IBM's 8-bit encoding.