Sony XTL-W70 用户手册

Press (V OFF) for two seconds.

You only hear the sound of the selected programme.
To cancel the visual off function, press (V OFF) again. If you
turn the unit off or turn the ignition switch to the OFF position,
the visual off function will be cancelled.

The visual off function is also canceled when you select another
TV programme with the programme number buttons (TV only).

When the visual off function is canceled, the screen mode
returns to “Full screen.”