12key

12key, also written 12-key keypad, refers to a compact keypad comprising twelve keys used for input in electronic devices. The standard 12-key layout forms a 3 by 4 grid, with digits 1 through 9 arranged in three columns, a 0 key, and two function keys, commonly star (*) and hash (#). In most devices the 0 is centered along the bottom row, with * and # at the bottom left and bottom right respectively.

Its primary use is numeric entry; many devices also map the digits to letters for text input (for example, 2 maps to ABC) using multi-tap or predictive systems such as T9. On phones and similar devices, the 12-key keypad is typically a physical keypad; in modern smartphones this functionality is often replaced by on-screen keyboards, though dedicated devices such as feature phones, calculators, and many point-of-sale terminals retain physical 12-key keypads.

Common applications include landline and mobile telephones, ATMs, payment terminals, access-controlled doors, and industrial instrumentation. The 12-key keypad is valued for its simple tactile feedback, compact size, and reliability in low-light or glove-wearing conditions. Some variants feature backlit keys, raised ridges for orientation, or nonstandard legends for localized use.

History and terminology: The 12-key layout evolved from the numerical keypad standard used in telephony and computer input. It rose to prominence with push-button telephones using DTMF signaling to dial numbers. In many devices, the 12-key arrangement is a subset of a larger keypad or a dedicated module rather than a full alphanumeric keyboard.