RCA look 15377550 - Manual (Page 45)

The Menu System
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A check mark next to the language choice means you have selected it as
your preferred option. The digital receiver will then set the audio
program to reflect this choice. For example, if you select French, the
digital receiver will then automatically set the audio track to French
whenever French audio is available.
Picture Format
Some television sets and home theater systems have screens that are
slightly wider than standard televisions. (This wider screen is sometimes
called a cinema screen). A normal TV has an aspect ratio of 4x3, while a
cinema screen has an aspect ratio of 16x9.
The Picture Size menu lets you to choose between a standard screen
(4x3 ratio) and the wider cinema screen (16x9 ratio). You should only
use the 16x9 option if you have a cinema screen TV. Using this option
with a standard screen TV may crop or distort the picture.
To choose a picture size:
1. Point to Picture Format in the Set-up & Test menu and press
SELECT•MENU.
2. Point to the type of TV screen you have and press SELECT•MENU.
When 16x9 is selected, 16x9 video will be displayed if it is available. If
not, 4x3 video will still be shown.