iPhone: Understanding the TTY symbol in the status bar
Learn how to identify the Teletype (TTY) symbol in your iPhone status bar, and how to turn TTY on or off.
If you see this symbol in the status bar, it means that TTY is on.
Teletype (TTY) machines are used by deaf and hard of hearing people to communicate by typing and reading text. If you have the iPhone TTY Adapter, available at www.apple.com/store, you can use iPhone with a TTY machine.
Choose Settings > Phone to turn TTY on or off.