For the hearing-impaired, email and chat work just fine in many cases that would otherwise require a phone call. Even so, there are times when you need to communicate more quickly.

This is exactly what the Real Time Text (RTT) protocol is for. RTT shows typing as it happens, allowing for near-instantaneous communication. It’s also built into both macOS and iOS, though it isn’t readily apparent. Fortunately, it’s easy to get set up.

Why You Might Need RTT Calls

Accessibility is one of the main reasons for the Real Time Text protocol, but it’s not the only one. There are plenty of other situations where it can come in handy.

If you work in an environment that is extremely noisy, but you still need to communicate quickly, Real Time Text calls can be quite useful. Real Time Text is also a much more accurate way to quickly exchange data like numbers or addresses. Since they allow you to communicate silently, RTT calls are also useful for passing sensitive data in public environments.

You can approximate many of these use cases with chat or email, but RTT works alongside voice calls. This means you can converse as you normally would, then quickly type in a number. There’s no need to switch to a different method of communication.

How to Use RTT Calls on macOS

RTT supported on iOS started with version 11.2, but they only came to Mac beginning with macOS Mojave 10.14.2. If you have a Mac from 2012 or later running this version of macOS or higher, you can make RTT calls. Unfortunately, Mac Pro models are an exception and don’t work with RTT.

In order to make RTT calls, you’ll also need an iPhone with a plan from AT&T, T-Mobile, or Verizon. Keep in mind that standard voice call rates apply during these calls.

Set Up RTT Calling on macOS

Before you get started, you’ll need to make sure you’ve set up Wi-Fi calling on your iPhone. You also need to enable making calls on other devices.

Now, open System Preferences and head to the Accessibility section. Assuming you’ve set up Wi-Fi calling correctly, you’ll see RTT in the sidebar under the Hearing section.

Select the checkbox labeled Enable RTT. By default, messages send in full. If you would prefer characters to appear as you type them, select Send Immediately. Finally, enter the RTT relay number to use. In the U.S., this is 711.

RTT Call settings on macOS

Make RTT Calls on macOS

Once you’ve got everything set up, making RTT calls on macOS is a fairly simple process. You’ll use FaceTime for calls, but you can also start RTT calls from the Contacts app.

To start an RTT call in FaceTime, click the call button, then choose RTT Call or RTT Relay Call from the menu.

To start an RTT call from Contacts, move the mouse over a phone number, then select the RTT icon. You saw this icon earlier while setting up RTT calls; it looks like a phone icon over a keyboard icon.

When the person on the other end answers, click the RTT icon to begin exchanging text messages. You can speak through the microphone as you do this, mixing and matching speech and text as you see fit. Clicking the RTT icon will hide it.

These instructions also work for answering RTT calls.

Making an RTT call on FaceTime

One cautionary note to beware of: some carriers will disconnect RTT calls if you haven’t exchanged any messages. Whether you can make RTT calls at all will depend on your carrier. RTT calling isn’t supported in all regions, so make sure to check the availability in your area.

How to Use RTT Calls on iOS

While RTT calling has been available on the iPhone longer than on macOS, it’s not a widely advertised feature. As long as you have an iPhone 6 or later with a plan from AT&T, T-Mobile, or Verizon, you’re equipped to make RTT calls.

Set Up RTT Calling on an iPhone

On your iPhone, open the Settings app, then scroll down to General. In this menu, select Accessibility. Here, scroll down until you find the RTT/TTY option under the Hearing section.

Enable Software RTT/TTY, and you’ll see some other options pop up. The Relay Number should be set by default. If it isn’t, set it to the number for your region. In the United States, this is 711.

You also have the option to Send Immediately, which shows characters pop up as you type. If you turn this option off, you can type an entire message before sending it. One other option is to Answer All Calls as RTT/TTY.

Making RTT Calls on an iPhone

Making RTT calls is as simple as making any other call. Open the Phone app, select a contact, and tap their number. Now instead of selecting Call [Name], select RTT/TTY Call or RTT/TTY Relay Call.

Wait for the call to connect, then select RTT next to the Keypad icon. You can also swap a call to RTT at any time. Simply tap Use RTT next to the End Call icon.

By default, RTT calls will keep the microphone active. To go text-only, tap the microphone icon in the top-right of the screen. To end a call, tap the Back button, then tap the End Call icon.

Making and Receiving RTT Calls on Other iOS Devices

You can also make and receive RTT calls on an iPad or iPod Touch. To do this, all you need to do is set up Wi-Fi Calling on your iPhone. Then make sure that the other device you want to use for RTT calling is enabled in the Allow Calls On section.

Other Secret Mac and iOS Features

Were you surprised to find out that RTT is built into both macOS and iOS? There’s a good chance that it’s not the only feature you’ve missed out on.