Change RTT preferences for accessibility on Mac
On your Mac, use the NRS pane of Accessibility preferences to set up your Mac to make and receive National Relay Service (NRS) calls.
To change these preferences, choose Apple menu > System Preferences, click Accessibility , then click RTT.
Note: These preferences are shown only when you have set up your iPhone and Mac for Wi-Fi calling and NRS relay calls are enabled on your iPhone. NRS is not available in all countries or regions, or supported by all service providers.
Make and receive NRS calls on your Mac without using a special device.
When this option is selected and you make a phone call on your Mac, you can choose to use audio, NRS or SMS relay for the call.
Send characters as you type them.
To type full messages before you send them, deselect this option.
SMS relay number
The relay service to use when you make an SMS relay call on your Mac.
If a number isn’t specified, your service provider’s default relay service is used.
When NRS relay calls are enabled on your Mac, the NRS button is shown — for example, in a card in the Contacts app or in FaceTime — to indicate that you can make an NRS call. Depending on your network environment, an NRS call may be downgraded to a TTY call.
Important: When making an emergency call in the US on your Mac, special characters or tones are sent to alert the operator. The operator’s ability to receive or respond to these tones can vary depending on your location. Apple doesn’t guarantee that the operator will be able to receive or respond to an NRS call.