FaceTime RTT phone call requirements

If you have difficulties hearing or speaking, or want to call someone who does, you can use Real-Time Text (RTT) for your phone calls, if your carrier supports it.

To make or receive an RTT call, make sure of the following:

• Your Mac has macOS 10.4.2 or later installed.

• Your iPhone has iOS 12.1.1 or later installed. See the Apple Support article Update your iPhone, iPad, or iPod touch.

• Your iPhone and Mac are on the same Wi-Fi network and connected to the internet.

• You’re signed in with the same Apple ID on your Mac and iPhone, and FaceTime is turned on in iCloud preferences or settings. See the Apple Support article Use Continuity to connect your Mac, iPhone, iPad, iPod touch, and Apple Watch.

• Your iPhone and Mac have Wi-Fi Calling turned on. Wi-Fi Calling isn’t available on some Mac models.

This feature is not available in all countries or regions or supported by all carriers. Depending on your network environment, an RTT call may be downgraded to a TTY call.

See the Apple Support article Make and receive RTT calls on your Mac.