T.50 (standard)

ITU-T recommendation T.50 specifies the International Reference Alphabet (IRA), formerly International Alphabet No. 5 (IA5), a character encoding. ASCII is the U.S. variant of that character set.

The original version from November 1988 corresponds to ISO 646. The current version is from September 1992.

History

At the beginning was the International Telegraph Alphabet No. 2 (ITA2), a five-bit code. IA5 is an improvement, based on seven-bit bytes.

• Recommendation V.3 IA5 (1968): Initial version, superseded
• Recommendation V.3 IA5 (1972): Superseded
• Recommendation V.3 IA5 (1976-10): Superseded
• Recommendation V.3 IA5 (1980-11): Superseded
• Recommendation T.50 IA5 (1984-10): Superseded
• Recommendation T.50 IA5 (1988-11-25): Superseded
• Recommendation T.50 IRA (1992-09-18): In force

Use

The IA5STRING string type in ASN.1 is restricted to characters in IA5. This standard is referenced by other standards such as RFC 3939 ("Calling Line Identification for Voice Mail Messages"). It is also used by some analog modems such as Cisco ones.

Character set

The following table shows the IA5 character set. Each character is shown with the code point of its Unicode equivalent.

Standardisation

• Identical standard: ISO/IEC 646:1991 (Twinned)

See also

• ITU T.51

References

External links

• Official ITU-T T.50 page
• Tech Info - Character Codes (IA5 and ISO 646)