From MobileDesign

The advantages of one-handed devices are obvious: the user can make a call while still carrying something. The trade-offs are that the keypad likewise has to be small, and text input will inevitably be slower than with devices you can devote two hands to. As a general rule, one-handed devices are phones. Phones need to be usable for dialing with the same hand holding and pressing buttons.

[edit] Hardware

[edit] 10-key (12-key)

This standard layout has the digits 0-9, *, and #, and allocates 2-4 letters to each of the keys 1-9. You have undoubtedly had several phones with this layout. More likely is that you have never had a phone with any other layout, unless you use a stylish phone in Japan.

Text entry is accomplished using "multi-tap", where the user presses a key repeatedly to cycle through the letters on the key. Thus the word "home" uses the following sequence: 4, 4, 6, 6, 6, pause, 6, 3, 3. The pause is necessary to ensure that the fourth 6 does not change the "o" to a "6" or "m" (depending on the device).

[edit] Fastap

This is a multi-level keyboard: if you press a number, you are actually activating the switches in the four surrounding buttons. Letters are spaced such that if you press one, no other buttons are pressed. The device can then determine the user intention. The primary advantage of this keyboard is the simple mapping: one button=one character. It is therefore possible to send a message without looking at the device. Digit Wireless Fastap

[edit] Delta II

The Delta II keyboard uses a large number of small keys to emulate a conventional typewriter or desktop computer keyboard. To account for the reduced width of conventional mobile phones, the keys are stacked (W is below Q, instead of next to it). This proximity is supposed to build on user's familiarity with existing keyboard layouts to improve speed. Numerous bits of test information on their website seem to bear out this speed claim, though none are apparently in production, so this is hard to verify. Chicago Logic Delta II

[edit] Helvedial

Helvedial is a 15-key pad, arranged like a conventional 10-key/12-key pad, with another row of buttons at the bottom. Each button is assigned two letters only, with * and # occupying two space spaces in the center. Presumably, numeric dialing will continue to function as usual, using only the top or bottom set of 12 keys.

[edit] SureType

RIM product based around a standard numeric keypad, with an additional column of keys on either side. Two letters are assigned to each key, instead of the 3-4 from typical keypads. In predictive typing mode, the directional pad or scroll wheel is used to select the correct word. [1]

[edit] Software

Many companies have developed "predictive" text input software. The predictive refers to predicting that a particular sequence of keystrokes was intended to be a particular word. Some software also has word completion. The most useful software has user-extendable dictionaries, frequency-mapping so that words used more frequently by that user pop up first, and are easily toggled off to allow typing, for example URLs or email addresses, and then on again for normal operation.

Also included here are keypads that, while mapped differently, are not mechanically different from conventional 10-key/12-key pads (the number of buttons is the same, and numeric characters can be entered without change).

[edit] Nuance (formerly Tegic) T9 Text Input

T9 is the oldest of the commonly used predictive spelling engines for mobile devices. The original company, Tegic, has been moved several times and is now a part of Nuance. The conventional key mapping is used, but predictive typing means that (in general) only one press per key is performed. Nuance T9, T9.com

[edit] Nuance XT9 Smart Input

This is an extension to the T9 product, adding on many features which are the hallmarks of competing, one-handed text entry products. The primary difference is of auto-completion, where the most obvious complete words are presented on screen. The user may select these words without completing a keypress per character as with conventional T9. Auto-completion is also available for the triple-tap entry method. Nuance XT9

T9 Nav is another associated Nuance product that enables search via predictive entry, with relevant search results forming the available words for the predictive language completion. Nuance T9 Nav

[edit] Eatoni WordWise

Eatoni also attacked the fundamental problem of text input, without resorting to a dictionary, word prediction, or a different keyboard. The result was WordWise. One letter was chosen on each button to require a modifier key; these are common letters that result in the other letters on the key being unlikely substitutions for each other.

To use the highlighted letter (one of CEHLNSTY), the user first presses the modifier key - in this case, the 1 key. To use any other letter, the user simply types the letter. The result is only 1 in 45 words are ambiguous, and for only 1 in 440 words the most likely interpretation is wrong. URLs and words not likely to be found in a dictionary are as easy to type as any other word. Eatoni WordWise

[edit] Eatoni LetterWise

The goal for LetterWise is for the user to type only one key for most letters in a word. For the first letter, the user taps the key, then a key indicating the letter's position on that key, then a designated "Next" key. For each subsequent letter, LetterWise chooses the most likely letter for that keypress. This dramatically reduces the number of keypresses per word. LetterWise may also be integrated with software keyboards. There is a separate Chinese-language variant of this product. Eatoni LetterWise

[edit] Zi Corporation eZiTap / eZiType

This software is word prediction and completion built on top of multi-tap. The user multi-taps the word until the software completes it, or one of the alternate words displayed is desired. Any word that the user types fully - whether spelled correctly or not - is added to the dictionary automatically, and the software updates the word frequencies to ensure that the user's common words are the default words predicted.

The software also learns vocabulary from the user's address book, browser, and other data stored on the device. Punctuation is handled almost automatically. Entering a number is a long keypress of the number (history suggests that users may not find this feature). Zi Corporation eZiType

[edit] Thumbscript

This solves the problem of multi-tap by mapping each letter and punctuation to a pair of keypresses. The pairs are assigned in a mnemonic way. On average this will require fewer keystrokes than multi-tap, but real speed is not possible until the software is built into a touch screen and thus gestures are possible. Of course, there are other solutions for handwriting recognition. See a demo at the Thumbscript site. Thumbscript

[edit] TenGo Thumb

For how the software works, see TenGo under Two-handed entry. We have placed this entrant here because it can convert a touch-screen device into, potentially, a one-handed device. That could turn out to be as important as the five-way rocker on the Palm Treo line, but only if the device software is smart enough to accept the input. [2]

[edit] Virtual Selection Systems

[edit] Virtual Keyboards

Some constrained-interface devices with only a scroll and select interface (such as GPS units and TV remotes) allow or require text entry via a virtual keyboard. Typing is via scrolling (with the 4-way/5-way pad) to the appropriate character, and pressing the enter/select button for each character. Implementation varies; some allow scrolling directly out of the keyboard to other functions, some enable wrap-around keyboard selection, so require an explicit exit from the the keyboard screen.

Virtual keyboards are more commonly, and successfully, used with pen or touch interfaces. See Two hands and a surface for more details.

[edit] Kannuu

This is a system of predictive typing, that uses the 4-way/5-way pad for entry, instead of the keypad. Users are presented with four options (and a 'next' function for additional options), and subsequent options build on those already entered. While really not suitable for general language entry – it is designed for constrained sets of information, such as picking from long lists – it is more akin to a text entry method than any of the design patterns under Listings.

This appears to be the same product as the N-e-ware Keystick, purchased modified and renamed by Kannuu, though this is not entirely clear. Kannuu