RTT stands for "Real-time Text" and is a feature that allows users to send text messages in real-time during a phone call. It is an accessibility feature that is particularly useful for people who are deaf, hard of hearing, deaf-blind, or have a speech-related disability. RTT calls can be initiated and received using the same ten-digit numbers used for voice calls, with standard rates applying depending on the carrier.

During an RTT call, both the caller and receiver have indications that they are in an RTT call. When connected, both sides enter the RTT call where the text input and keyboard is activated. When typing, the text appears and is sent as it is typed, character by character. RTT calls include an audio stream, and users can mute or unmute their microphone.

To use RTT, users need to turn it on in their phones settings. Once enabled, users can switch to RTT during a call, whether they started or received the call. During an RTT call, users can merge, hold, or switch to voice, and they can have multiple RTT calls going at the same time.

RTT eliminates the need for users to buy specialized tools to send real-time texts on wireless phones, and it gives them great flexibility and accessibility when using wireless devices.