 Closed-circuit television (CCTV) systems are used to produce and display enlarged images of any type of reading material, including printed text, handwritten text, photos, diagrams, charts, and maps. The basic CCTV system has three components, a video camera with a zoom lens and a light source, a monitor, and a viewing table. The user places the reading material on a movable viewing table, and an enlarged image is projected on the monitor. CCTVs allow the user to vary the degree of magnification; adjust brightness, clarity, and contrast; and change the polarity of the display from positive (black text on white background) to negative (white text on black background). One major advantage of some CCTV systems is that they can be used for both reading and writing tasks. Most of these systems are black and white, but some color systems are available. Also, some CCTV systems work in conjunction with computers and display magnified text on the monitor.
TeleSensory
Seeing Technologies
HumanWare
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