- 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.