Two-Thumb Keypad Chording
When designing a text entry system for mobile phone keypads, a designer needs to overcome the ambiguity that arises from mapping the 26 letters of the roman alphabet to only 12 keys (0–9, *, #). I created a novel two-thumb chording system for text entry on a standard 12-key mobile phone keypad and a performance model based on Fitts’ Law for an expert user. The model provides a behavioral description of the user and predicts a text entry rate of 55.02 wpm.
Our method consists entirely of one and two-key chords using only the standard 12 keys found on mobile phone keypads. Keys 2–9 are used as character keys while the *, 0, # and 1 keys are used as chording keys. By pressing any of the character keys alone the user enters the first letter displayed on the key. Simultaneously pressing a character key in combination with the * key allows the user to enter the second letter displayed on the key, pressing a character key with the 0 key enters the third character and pressing a character key with # key enters the fourth character in the case of “s” and “z”. The space character is entered by pressing the # key alone. The table below shows the keymap for generating all of the letters and the space character. Numbers are entered by using the 1 key as a chording key to select the numeral on the key. By pressing 1 alone, the user enters 1. By pressing 1 in combination with any other number, the user enters that number. Capitalizing a letter is performed by first pressing the 0 key alone and then entering the character. Rapidly pressing 0 twice allows the user to enter caps-lock mode, pressing 0 again once reverts to the previous mode. Common symbols can be accessed by pressing the # key and character keys other than 7 or 9.
Poster. Georgia Tech Undergraduate Research Symposium.
Phong Su Si, Nirmal Patel and Thad Starner.
Best Poster Award for College of Computing