November 13, 1994
Hello again to members and friends of the NFB R&D Committee,
I read Steve's comments with great interest. If we wish
to endow our scientific calculator with the ability to produce
graphs in print or on the screen, I agree with his reasoning.
My plans for the calculator, however, were not that ambitious.
But what Steve proposes certainly has merit. Eventually, however,
we will have to face the problem of 300 dots per inch in print or
on the screen vs. 11 dots per inch on a braille embosser, whether
we do it up front as I did, or later, after producing a print
graph, as Steve proposes. What do the rest of us think? Should
our calculator have the capability of outputting a graph on a
printed page or on the screen?
There is a form of
braille called microbrl in which the dot
pitch is 0.08 dots per inch instead of 0.09 dots per inch. You can
see this kind of braille on the labels of the cassettes you receive
from the Library of Congress. However, this increases the
resolution from 11 dots per inch to just over 12 dots per inch --
not a quantum leap.
A spur wheel is a much better tool for producing a graph than
an embosser. At present, however, a spur wheel must be guided by
hand. I can imagine a mechanical device that guides a spur wheel.
The device can be "instructed" to advance the spur wheel one pin
in the direction in which it is facing to form the next dot on the
page, after which it can be "instructed" to pivot on that pin by a
specified small angle before advancing to the next pin. In this
way, by alternating between these two instructions -- "advance"
and "pivot" -- the spur wheel can produce a raised-line graph much
finer and more accurate than a graph produced on a braille
embosser. The ability to pivot through a controlled angle is what
makes a spur wheel so much more accurate than an embosser that
lacks this capability. However, no such device exists nor, to my
knowledge, is being contemplated.
Abraham Nemeth, Ph.D.
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