Samsung SM-S921B User Manual page 130

Apps and features
Using Samsung DeX and mobile device simultaneously
While using Samsung DeX, you can use separate apps on the external display and your
mobile device simultaneously.
For example, while watching a video on the connected TV or monitor, you can chat with
your friend on a messenger.
On the connected TV or monitor, open an app to run on the Samsung DeX screen. Then,
open another app on your mobile device.
Locking the Samsung DeX screen
If you want to lock the Samsung DeX screen and your mobile device's screen while using
Samsung DeX, select
While using Samsung DeX, you cannot lock the Samsung DeX screen and your
mobile device's screen by pressing the Side button.
→ Lock DeX.
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