E.161 is an

ITU-T The ITU Telecommunication Standardization Sector (ITU-T) is one of the three sectors (divisions or units) of the International Telecommunication Union (ITU). It is responsible for coordinating standards for telecommunications and Information Co ...

Recommendation that defines the arrangement of digits, letters, and symbols on telephone keypads and rotary dials. It also defines the recommended mapping between the basic Latin alphabet and digits (e.g., "DEF" on 3). Uses for this mapping include: *

Multi-tap Multi-tap (multi-press) refers to a text entry system for mobile phones. The alphabet is printed under each key (beginning on "2") in a three-letter sequence as follows; ABC under 2 key, DEF under 3 key, etc. Exceptions are the "7" key, which ...

and

predictive text Predictive text is an input technology used where one key or button represents many letters, such as on the numeric keypads of mobile phones and in accessibility technologies. Each key press results in a ''prediction'' rather than repeatedly ...

systems. * Forming phonewords from telephone numbers. * Using alphabetic characters (e.g. as a

mnemonic A mnemonic ( ) device, or memory device, is any learning technique that aids information retention or retrieval (remembering) in the human memory for better understanding. Mnemonics make use of elaborative encoding, retrieval cues, and image ...

) in a

personal identification number A personal identification number (PIN), or sometimes redundantly a PIN number or PIN code, is a numeric (sometimes alpha-numeric) passcode used in the process of authenticating a user accessing a system. The PIN has been the key to facilitati ...

. Keypads are specified both in the common 4 × 3 and several variations, such as 6 × 2 and 2 × 5. E.161 also specifies the dimensions and characteristics of the

asterisk The asterisk ( ), from Late Latin , from Ancient Greek , ''asteriskos'', "little star", is a typographical symbol. It is so called because it resembles a conventional image of a heraldic star. Computer scientists and mathematicians often voc ...

and

square In Euclidean geometry, a square is a regular quadrilateral, which means that it has four equal sides and four equal angles (90- degree angles, π/2 radian angles, or right angles). It can also be defined as a rectangle with two equal-length a ...

, referred to in the standard as the 'star' and 'square' keys, respectively. (In practice, the 'square' key is almost invariably replaced by the

number sign The symbol is known variously in English-speaking regions as the number sign, hash, or pound sign. The symbol has historically been used for a wide range of purposes including the designation of an ordinal number and as a ligatured abbreviati ...

.) The standard also recommends that a tactile identifier be placed on the 5 key to make it easier to use the keypad in low-light conditions or by the

visually impaired Visual impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment� ...

, as well as multiple alternative methods to implement a recall button.

ETSI The European Telecommunications Standards Institute (ETSI) is an independent, not-for-profit, standardization organization in the field of information and communications. ETSI supports the development and testing of global technical standard ...

ETS 300 640 and ISO 9995-8 also address keypad layout. Language-specific letters (e.g. ü, é, å, ä, ö) as well as other characters (e.g. ‘€’ or ‘@’) are not addressed, which has led to a variety of inconsistent solutions for European languages. The E.161 layout is primarily based on the layout used on American telephones since the 1930s for

telephone exchange names A telephone exchange name or central office name was a distinguishing and memorable name assigned to a central office. It identified the switching system to which a telephone was connected, and facilitated the connection of telephone calls betwee ...

. Until the 1990s, Q and Z were not included in the standard layout, and since the letters served mainly as mnemonic devices, they were not necessary (Q and Z were not used in

phoneword Phonewords are mnemonic phrases represented as alphanumeric equivalents of a telephone number. In many countries, the digits on the telephone keypad also have letters assigned. By replacing the digits of a telephone number with the correspondin ...

s); telephones either omitted them, placed Q and Z onto the 1 key, or included Q and Z on the current locations, with PRS on 7 and with WXY on 9, respectively. The development of

text messaging Text messaging, or texting, is the act of composing and sending electronic messages, typically consisting of alphabetic and numeric characters, between two or more users of mobile devices, desktops/laptops, or another type of compatible comput ...

on mobile phones, which required the full range of the alphabet, led to the need to standardize locations for Q and Z on mobile devices. E.161 adopted the current layout in response to this.

Notes

References

External links

* {{cite web , url= http://www.itu.int/rec/T-REC-E.161/en , title= E.161 Arrangement of digits, letters and symbols on telephones and other devices , id= E.161 , orig-year= 1988 , date= Feb 2, 2001 , publisher=

International Telecommunication Union The International Telecommunication Union is a specialized agency of the United Nations responsible for many matters related to information and communication technologies. It was established on 17 May 1865 as the International Telegraph Unio ...

(ITU) Telephone numbers Identifiers ITU-T E Series Recommendations