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Figure 3. FastTap™ phone keyboard
handed chord keyboards. One-handed chord
keyboards are by definition palm-sized and were
originally envisaged as the ideal partner to the
mouse (Engelbart & English, 1968), allowing
users to enter text and point at the same time.
Single-handed chord keyboards have been used
in mobile devices (Figure 4 shows the AgendA
organiser including an alphabetic keyboard sur-
rounded by a chord keyboard). However, the
learning time is prohibitive with few users willing
to learn the chords required to use these keyboards.
Furthermore, the keyboards are not usable with-
out training—users cannot guess how to use them
when first picking up a device. Thus, despite size
and speed advantages, chord keyboards are gen-
erally considered too alien for main-stream de-
vices and rarely appear on consumer products.
Ambiguous Keyboards
The most common ambiguous keyboard, and the
dominant keyboard for mobile phones, is still
the telephony ISO/IEC standard 12-key phone
keypad (e.g. Figure 5). Originally envisaged for
name-based dialling of telephone area codes,
this keyboard is labelled with groups of three
or four letters on each of the physical keys 2
A drastically different unambiguous keyboard
approach is to use chords—multiple simultaneous
key-presses mapping to a single character, either
using one or both hands. Chord keyboards can
give extremely fast entry rates, with court stenog-
raphers reaching around 225wpm using a two-
Figure 4. Sample chord keyboards (Douglas Engelbart and Microwriter AgendA)
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