But you probably don't know how the system works. Well, here's a brief overview. Closed captioning translates the audio portion of a television program into subtitles. These subtitles, also called captions, let hearing-impaired viewers read what they cannot hear.
Captions usually appear at the bottom of the TV screen as white letters on a black background.
The size of the letters varies with the size of the TV screen. On a nineteen inch screen, for example, letters are half an inch high. Not all programs are produced with closed captioning. Currently, more than seventy hours of television programs are closed-captioned each week. Programming includes movies, network news, sports events, children's and educational programs.