Why does my iPhone 4 have a lock with a circle around it on the screen?

[iMore Question]

why does my iPhone 4 have a lock with a circle around it on the screen

my iPhone 4 does not always ring and has a lock with a circle around it on the top right of the screen.

 

[Sakroz]

Re: why does my iPhone 4 have a lock with a circle around it on the screen

my iPhone 4 does not always ring and has a lock with a circle around it on the top right of the screen.

lock with a circle around means rotation lock is on, as for the ringing perhaps mute switch getting turned on accidentally?

 

[kataran]

Re: why does my iPhone 4 have a lock with a circle around it on the screen

To turn off the lock just access the Control Center by swiping up from the Home screen and disable by tapping on the icon on the top right