In my closed caption menu, there is 4 options. C1, C2, T1, and T2. I know the C1 and 2 is caption, but whats T?

When I select the t1, it just brings up a black box in the middle of the screen, with nothing in it. I've always wondered what this was.In my closed caption menu, there is 4 options. C1, C2, T1, and T2. I know the C1 and 2 is caption, but whats T?
T1 and T2 stand for Text 1 and Text 2; they're not used that often, but allow for extra captions (multi-lingual captions, subtitles, different channels). the black box indicates that bandwidth is reserved for text captioning in the broadcast, but it isn't used.





Some programs may also have C3 and C4 channels for captions... most TV sets support C1 and T1, some support C1/C2 and T1/T2, very few use C3 and C4.





http://en.wikipedia.org/wiki/Closed_capt鈥?/a>