You can use the iPhone TTY Adapter cable (sold separately in many areas) to connect iPhone
to a TTY machine. Go to www.apple.com/store (may not be available in all areas) or check with
your local Apple retailer.
Connect iPhone to a TTY machine: Go to Settings > Phone and turn TTY on, and then connect
iPhone to your TTY machine using the iPhone TTY Adapter.
When TTY is enabled on iPhone, the TTY icon appears in the status bar at the top of the
screen. For information about using a particular TTY machine, see the documentation that
came with the machine.