Non Optical Devices
Other devices that can be obtained include coin holders,
talking clocks and watches, stick on raised pads for dials, large
print telephone dials, writing frames and typographs. The latter
is basically a matt black card into which a rectangular hole is
cut to allow writing through. They are available commercially for
writing and also tailored to specific needs such as cheque writing.
The other main category of non-optical device is the
CCTV (Closed Circuit Television) system.The basic principal behind
these types of unit involves a small camera being used to ‘view’
the reading matter. The image generated is then converted into a
television signal that can be projected onto either a television
screen or dedicated monitor. The sophistication of this type of
device ranges from a basic monochrome camera mounted within a small
handheld ‘mouse’ that is run over text manually through to full
colour systems featuring high quality stand mounted cameras, moveable
reading tables and true colour monitors.
The principal advantage of these systems is the virtually
unlimited magnification possible with little or no image distortion.
Maximum magnifications can be as high as 30x although the actual
benefit of this high degree of magnification may be limited through
the quality of the print. Another advantage demonstrated with these
units is the ability to reverse colours so that in place of black
text on a bright white background you could switch to black background
with white text.
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