Sharp LC-20B4M Service Manual page 17

8. SOUND ONLY MODE (NO↔YES)
(* This item cannot be selected if "NO" appears on the on-screen display.)
Let's suppose that this item has been selected and the BRIGHT key on the remote control has been pressed.
The item "BRIGHTNESS [OFF]" can now be selected next to the item "BRIGHTNESS [DARK]".
Screen with "BRIGHTNESS [OFF]" selected
BRIGHTNESS [OFF] TURNS OFF IN 5 SECS.
Five seconds later, the screen shuts off and the sound alone is heard.
Once in this mode, no picture but the OSD appears. But the channels and sound volume can still be changed.
To quit this mode, press the BRIGHT key on the remote control again and select any item other than
"BRIGHTNESS [OFF]".
9. RESET
You can cancel all Public Mode settings. (It returns to the factory setting.)
10.ENTER
You make sure after you have specified all functions, then press the enter key. Unless otherwise you press
the enter key, all positions that you have selected will not be set.
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LC-20B4M