Keyboard
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Keytops and spacing
Designed to be comfortable for the user's fingers, keys typically have a top
surface that is about half an inch square on a threequarterinch center and
have a slightly concave surface. Home position keys may be more concave than
the others so that the typist can sense by touch that the fingers are properly
placed. Keytops may have a matte finish to prevent reflections from overhead
light sources, making their labels easier to read. The matte finish also makes
the keytop less slippery. Keytops consisting of dark lettering on a light background
are generally preferred.
Many who discuss the subject of specular reflections from equipment surfaces,
such as keytops, talk about the surfaces as "matte"finished. In fact,
ISO 9241 - Part 4 specifies that
"The visible surfaces of the keytops shall be matt finish."
In addition, ISO recommends that
"The diffuse reflection of the alphanumeric keytops should have values
between 0,15 and 0,75"
On the same topic, the BSR/HFES 100 Draft Standard stats that the
" Specular reflection (gloss) of visible surfaces .......... Should
be 45% or less."
Keyboard packaging
The basic objectives in keyboard packaging are to minimize size of the unit,
yet provide for logical key layout and create a proper slope. Minimizing size
is important because it means more room for other items on the work surface.
(Also, minimizing keyboard thickness and height permits maximizing knee space
below.) Slopes of 10 to 15 degrees are typical, but other slopes (Emmons and
Hirsch, 1982) may be considered for specific applications and locations.
Both ISO 9241 - Part 4 and the BSR/HFES 100 draft standard state that the
keyboard slope shall be between 0 and 15 degrees. Some research has shown user
preferences for even greater slopes (Emmons and Hirsch, 1982; Miller and Suther,
1983, Burke, etal. 1984). ISO contains a requirement that the home row height
of the keyboard shall not exceed 35 mm with the preferred home row height not
exceeding 30mm. BSR/HFES 100 draft standard recommends
" .....that keyboard slope be designed or adjusted.... to promote
wrist postures as close to straight as possible (e.g., within 5 degrees up
or down)."
The aim of such specifications is to provide guidance that reduces user
strain and fatigue and promotes good postural practices.
Other user considerations may be incorporated into the keyboard package so
long as they do not interfere with basic operations or make positioning the
keyboard more difficult. For example, if a palm or wrist rest is added, it
should be designed so that it does not interfere with normal keying.
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