What does this icon mean again ?

[galaxy121]

So I have this icon on the top right of my screen. I used to remember what it means and why it shows up but now I forgot. I mean the icon of the phone and 2 lines underneath it. What does this mean again ?

 

[EricNau]

That symbol means TTY is enabled. This setting is located in Settings > Phone.

http://support.apple.com/kb/HT3519