An RTT call is a phone call that uses real-time text, a technology that transmits each character of text instantly as you type it, without requiring you to hit a “send” button. The other person on the call sees your words appear on their screen letter by letter, as you compose them. RTT was designed primarily as an accessibility feature for people who are deaf, hard of hearing, or have speech disabilities, but it’s built into most modern smartphones and available to anyone.
How RTT Works During a Call
When you place or receive an RTT call, your phone opens a text interface that looks similar to a messaging app. The key difference from regular texting is that there’s no delay waiting for a composed message. Each character travels to the other person’s screen the moment you type it. Both people can type and read simultaneously, making the conversation feel more like a natural back-and-forth dialogue than an exchange of individual messages.
RTT calls use your phone’s regular ten-digit number. You don’t need a special number, a separate app, or any additional equipment. The call travels over your carrier’s IP-based network, the same infrastructure that handles your normal voice calls on modern wireless systems.
RTT vs. Regular Texting
Standard text messages (SMS) require you to finish typing and press send before the other person sees anything. RTT removes that step entirely. The recipient reads your message as you create it, character by character. This makes RTT feel closer to a live conversation than a text thread, which is why it’s categorized as a call rather than a message.
RTT also supports a much broader set of characters than older accessibility technologies. You can use emojis, the “@” symbol, and alphabets in multiple languages, giving you the full international character set rather than the limited set available on legacy devices.
How RTT Replaced TTY
Before RTT, people who needed text-based phone communication relied on TTY (text telephone) devices. These were standalone machines that required both callers to own compatible hardware. TTY also forced a turn-taking format, meaning only one person could type at a time, and it was prone to garbled text and dropped connections over modern IP networks.
RTT solved all of those problems. Both parties can send and receive text at the same time. No special device is needed since the feature runs directly on your smartphone. And because RTT was built for IP networks from the start, it’s more reliable than TTY, with fewer transmission errors. The FCC adopted rules in 2016 permitting wireless carriers and phone manufacturers to support RTT in place of TTY, and a phased rollout ran through 2021.
How to Turn RTT On or Off
On an iPhone, go to Settings, then Accessibility, then RTT/TTY. Toggle on “Software RTT” to enable the feature. From there you can choose whether to send each character immediately as you type or wait until you finish composing before transmitting. You can also set your phone to answer all incoming calls as RTT calls, which is useful if you rely on text-based communication for every call.
On Android phones, the setting is typically found under Settings, then Accessibility, then RTT. The exact menu path varies slightly by manufacturer and Android version, but searching “RTT” in your phone’s settings search bar will usually find it quickly. Most Android devices let you choose between RTT being always on, visible only during calls, or off entirely.
If you’ve never enabled RTT and you see “RTT call” appear on your screen, it likely means the person calling you is using the feature on their end, or your phone’s accessibility settings were toggled on unintentionally. You can disable it through the same settings path.
RTT and 911 Emergency Calls
RTT works with 911 and 711 (the relay services number). The FCC required that RTT users be able to reach emergency services, and in 2021 the agency expanded its text-to-911 registry to include real-time text. This means if you can’t speak during an emergency, you can place an RTT call to 911 and communicate by typing in real time, provided your local 911 center supports the technology. Coverage has expanded steadily, but not every emergency call center has adopted it yet.
Who Uses RTT Calls
RTT is most commonly used by people who are deaf or hard of hearing, people with speech disabilities, and anyone who needs or prefers text-based communication during a live call. It’s also useful in situations where speaking out loud isn’t safe or practical, such as during an emergency when you need to stay quiet.
Because RTT uses your phone’s existing calling function and regular phone number, it doesn’t require any additional cost beyond what you already pay for your wireless plan. There’s no separate subscription or special equipment to buy.