Keyboard
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Keyboard
In some applications, the user must perform rapid and accurate keying operations
while looking almost exclusively at a source document. In such cases, the keyboard
is the critical interface between user and system. Therefore, the way the keyboard
is laid out, how it functions and the design of the keys may affect user productivity
and acceptance.
Advancements in keyboard technology now permit a wide latitude in keyboard design.
For example, the minimum time between keystrokes is much less, and more than
one key may be depressed at any one time, There also is greater latitude in key
arrangement (Hirsch, 1970; Michaels, 1971).
Mechanical keyboards had some advantages. They often provided feedback of
sensory cues to the user, and the keyboard could be "locked" when
necessary. To give the user similar capabilities in electronic keyboards, those
characteristics must be build into or compensated for in the design. One approach
has been the generation of an audible "click" to indicate that a
signal from a depressed key has been received by the system. Conversely, inhibition
or accentuation of the auditory feedback may be used to signal the user that
the keyboard is "locked."
Rapid keying is a complex psychomotor process. A stream of coordinated signals
is sent by the brain to control the muscle activity that results in key actuations.
Several separate muscle activities may be going on at once: one finger may
be completing a key depression while a second is beginning one and a third
is moving toward a key to be depressed. While this is occurring, receptors
in the fingers are sending signals that carry information about the finger
movement back to the brain. This information (feedback) is correlated with
what the user has anticipated as proper feedback.
The ISO 9204 - Part 4 specification concerning keying feedback is:
"Actuation of a key shall be accompanied by feedback. Feedback can be
kinaesthetic, auditory or some combination of them. If the design allows
only one method, then kinaesthetic feedback is preferred."
Smooth, reflexive keying depends on a user's ability to generate a pattern
of motor signals and to receive information from the fingers so that a match
may be made between intended and perceived activity. That is why positive
feedback from the keyboard is important for accurate and rapid keying.
Of course, more than just good feedback is required for an efficient keyboard.
Layout, key spacing, the shape of the keytop, the ability to locate the hands
without visual guidance, size and provisions for hand rest or arm support are
important considerations for user efficiency and comfort.
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