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Baudot Code (ITA2)

5-bit character encoding used in early teleprinters and telegraph systems. Uses two modes (LETTERS and FIGURES) selected by special shift characters. Educational implementation of International Telegraph Alphabet No. 2 (ITA2/CCITT-2). ITA2 has only 32 five-bit code points per mode and no concept of letter case, so it can only represent the exact uppercase letters, digits, and punctuation listed in its LETTERS/FIGURES tables (plus space, CR, LF and NUL) - any other byte, including lowercase letters and arbitrary binary data, is rejected rather than silently folded or dropped.

Properties

Property	Value
Category	Encoding Schemes
Sub-category	Telegraph Encoding
Security status	🎓 Educational Only
Complexity	Beginner
Inventor	Émile Baudot
Year	1874
Origin	🇫🇷 France
Restricted input domain	Yes
Source	algorithms/encoding/baudot.js

Security

Status: 🎓 Educational Only

No vulnerabilities are recorded for this implementation.

Documentation

• ITU-T Recommendation F.1
• CCITT-2 (ITA2) Specification
• Telegraph History

References

• International Telegraph Alphabet
• Early Teleprinter Systems
• Baudot Code Analysis

Test vectors

4 vectors ship with this algorithm and run in the test suite. Byte values are hexadecimal.

Vector 1 — Baudot empty string test

Field	Value
input	(empty)
expected	(empty)

Vector 2 — Single letter A test - Baudot ITA2

Field	Value
input	41
expected	03

Vector 3 — Letter E encoding test - Baudot

Source: ITU-T F.1 standard

Field	Value
input	45
expected	01

Vector 4 — NUL-A-NUL regression test - code point 0 (‘\0’) must round-trip; it was previously unencodable because ‘\0’ is falsy in JavaScript

Field	Value
input	004100
expected	000300

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