Thanks for the tip re the CC option for my cable box. Apparently, my cable box does not offer that option and, based on my conversation today with Comcast, I'll have to trade my current DVR box for one with the added CC TV option. This is a bit of a hassle since, as you probably know, it is "unauthorized" for a customer to telephone a Comcast store, even if the number were not secret--which it is.
The Comcast tech said I should visit the Comcast store (about 7 miles from my home) and, if they have a newer, CC TV-equipped box in stock, ask to have it reserved for me, go back home, bring in the old box and trade for the new box.
This is not going to be worth this hassle, I suspect, so I'll see if I can pass up this great opportunity.