How to disable TalkBack when the screen is dim

The screen is dimmed, but it’s still displayed.
TalkBack is an accessibility service that helps vision-impaired people.  After selecting it, you can follow the audible prompts which guide you in clicking the icons. You can turn off the TalkBack function by following these steps:

1. Press Home button on remote.
2. Press ↓ (Down arrow) several times, and select Settings.
3. Press ↓ (Down arrow) 2 times.
4. Press → (Right arrow) several times, and select Accessibility.
5. Press ↓ (Down arrow) one time, and select Services.
6. Press ↓ (Down arrow) one time, and select Talkback on.
7. Select State on, then voice says on.
8. Press ↓ (Down arrow) one time, then voice says off.
9. Press Enter, then voice says OK.
10. Press Enter.

NOTE：This issue does not occur when TalkBack is updated to ver 4.1 or later from Google Play Store.