E.161 is an

ITU-T The International Telecommunication Union Telecommunication Standardization Sector (ITU-T) is one of the three Sectors (branches) of the International Telecommunication Union (ITU). It is responsible for coordinating Standardization, standards fo ...

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

mnemonic A mnemonic device ( ), memory trick or memory device is any learning technique that aids information retention or retrieval in the human memory, often by associating the information with something that is easier to remember. It makes use of e ...

) in a

personal identification number A personal identification number (PIN; sometimes RAS syndrome, redundantly a PIN code or PIN number) 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 faci ...

Keypads A keypad is a block or pad of buttons set with an arrangement of digits, symbols, or alphabetical letters. Pads mostly containing numbers and used with computers are numeric keypads. Keypads are found on devices which require mainly numeric in ...

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 , , "little star", is a Typography, typographical symbol. It is so called because it resembles a conventional image of a star (heraldry), heraldic star. Computer scientists and Mathematici ...

and

square In geometry, a square is a regular polygon, regular quadrilateral. It has four straight sides of equal length and four equal angles. Squares are special cases of rectangles, which have four equal angles, and of rhombuses, which have four equal si ...

, 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 as the number sign, hash, (or in North America) the pound sign. The symbol has historically been used for a wide range of purposes including the designation of an ordinal number and as a Typographic ligature, ligatured abbre ...

.) 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 or vision impairment (VI or VIP) is the partial or total inability of visual perception. In the absence of treatment such as corrective eyewear, assistive devices, and medical treatment, visual impairment may cause the individual difficul ...

, 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 operating in the field of Information and communications technology, information and communications. ETSI supports the de ...

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 telephone exchange, central office. It identified the switching system to which a telephone was connected, and facilitated the connection of te ...

. 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 WXY on 9. 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 phones, tablet computers, smartwatches, desktops/laptops, or ...

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 (ITU)In the other common languages of the ITU: * * is a list of specialized agencies of the United Nations, specialized agency of the United Nations responsible for many matters related to information ...

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