Closed captioning.....you know how when you're watching TV and right before the show a voice says "closed captioning provided by......" and you'll see a symbol that looks like this...
or this.....
and the words spoken appear on the TV screen like this....
It's a service provided for the hearing impaired.....
Closed circuit TV is a system that is recording and showing what's going on in a particular place....for example, the bank of TV sets you see in the security office of a business, that is showing what is going on in various areas of the building.
Or when you walk in a Walgreens and can see youself on a TV screen, and you check yourself out to see how fat you are.