On February 20, 2014, the Federal Communications Commission (FCC) unanimously approved standards defining the components necessary for high quality closed captions on television. The new standards explain that to be fully accessible, closed captions on television programs must accurately convey dialogue and sounds in the program, and run from the beginning to the end of the program.

Link: http://transition.fcc.gov/Daily_Releases/Daily_Business/2014/db0221/DOC-325695A1.pdf