E.161 is an ITU-T

ITU-T

The ITU Telecommunication Standardization Sector is one of the three sectors of the International Telecommunication Union ; it coordinates standards for telecommunications....

 recommendation that defines the assignment of the basic 26 Latin letters (A to Z) to the 12-key telephone keypad

Telephone keypad

A telephone keypad is a keypad that appears on a "Touch Tone" telephone. It was standardised when the dual-tone multi-frequency system in the new push-button telephone was introduced in the 1960s, which gradually replaced the rotary dial....

. Uses for this mapping include:

• Multi-tap
  Multi-tap
  Multi-tap refers to a text entry system for mobile phones.The alphabet is printed under each key in a three-letter sequence as follows; ABC under 2 key, DEF under 3 key, etc. Exceptions are the "7" key, which adds a letter , and the "9" key which includes "Z"...
  
   and predictive text
  Predictive text
  Predictive text is an input technology used where one key or button represents many letters, such as on mobile phones and in accessibility technologies. Each key press results in a prediction rather than repeatedly sequencing through the same group of "letters" it represents, in the same,...
  
   systems
• Forming phonewords from telephone numbers
• Using alphabetic characters (e.g. as a mnemonic
  Mnemonic
  A mnemonic , or mnemonic device, is any learning technique that aids memory. To improve long term memory, mnemonic systems are used to make memorization easier. Commonly encountered mnemonics are often verbal, such as a very short poem or a special word used to help a person remember something,...
  
  ) in a personal identification number
  Personal identification number
  A personal identification number is a secret numeric password shared between a user and a system that can be used to authenticate the user to the system. Typically, the user is required to provide a non-confidential user identifier or token and a confidential PIN to gain access to the system...
  
  

ETSI

European Telecommunications Standards Institute

The European Telecommunications Standards Institute is an independent, non-profit, standardization organization in the telecommunications industry in Europe, with worldwide projection...

 ETS 300 640 and ISO 9995-8

ISO/IEC 9995

ISO/IEC 9995 Information technology — Keyboard layouts for text and office systems is an ISO standard defining layouts of computer keyboards. It defines a keyboard as having three groups of key assignments:...

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.

External links

• E.161 Arrangement of digits, letters and symbols on telephones and other devices