Settings Menu; A/V Output; Aspect Ratio - D-Link DSM-750 User Manual

Section  - Configuration
The following options are available under the Settings menu:

A/V Output

Network
Under the A/V Output menu, you may change the Aspect Ratio to
either 4:3 (Standard Televisions) or 16:9 (Widescreen Televisions).
Please make sure you understand the ratio of your television screen
before changing the aspect ratio, or you may get a distorted picture.
D-Link DSM-750 User Manual

Settings Menu

Slideshow
System
A/V Output

Aspect Ratio

Extender