RTT stands for Real-Time Text, which is a feature that allows you to use text to communicate during a phone call. It is an accessibility feature that is particularly useful for people who are deaf or hard of hearing, as it allows them to have real-time conversations over the phone. RTT works with TTY (teletypewriter) and doesnt require any additional accessories. To use RTT, you need to turn it on in your phones settings. Once its turned on, you can place a call with RTT or switch from voice to RTT during a call. During an RTT call, the text is transmitted instantly and in real-time as it is typed, usually without clicking the send button. RTT calls use call minutes, just like a voice call.