E.161

E.161 is an ITU-T recommendation that defines the assignment of the basic 26 Latin letters (A to Z) to the 12-key telephone keypad. Uses for this mapping include:

• Multi-tap and predictive text systems
• Forming phonewords from telephone numbers
• Using alphabetic characters (e.g. as a mnemonic) in a personal identification number

ETSI ETS 300 640 and ISO 9995-8 also address this. Language-specific letters (e.g. ü, é, å, ä, ö) as well as other characters (e.g. ‘€’ or ‘@’) are not addressed and has led to a variety of inconsistent solutions for European languages.