Use the lock screen
To protect personal information, you can adjust your phone's lock settings:
1From the Home or All Apps screen, touch the Settings icon 
.
2Scroll down and touch Security.
3Touch Screen lock.
4Touch the type of lock you'd like to use.
After you set a lock here, a lock screen displays whenever your screen wakes up, requesting the pattern, PIN, or other specified key.
Important Screen lock options are listed in the approximate order of the strength of their security, starting with None and Slide, which provide no security. Face Unlock and Pattern provide minimal security, although they can be more convenient than the stronger options.
If your phone's playing music when the screen locks, you can continue listening or pause the selection without unlocking.
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