47 CFR § 76.606
Closed captioning
February 16, 2021
(a) The operator of each cable television system shall not take any action to remove or alter closed captioning data contained on line 21 of the vertical blanking interval.
(b) The operator of each cable television system shall deliver intact closed captioning data contained on line 21 of the vertical blanking interval, as it arrives at the headend or from another origination source, to subscriber terminals and (when so delivered to the cable system) in a format that can be recovered and displayed by decoders meeting §79.101 of this chapter.
[83 FR 7629, Feb. 22, 2018]