# RTT and TTY on iPhone: How It Works URL: https://byshahid.com/blog/rtt-and-tty-iphone/ App: Secret Codes: IMEI & Carrier (https://apps.apple.com/us/app/secret-codes-imei-carrier/id6807154322) Author: Muhammad Shahid Updated: 2026-11-04 > Text-based calling for accessibility. Real-Time Text sends characters as you type them during a call, so the other party reads along live. All four major US carriers support RTT, and it works with 911. - **What it does:** Text-based calling for accessibility. - **Published for:** any iPhone, Verizon, AT&T, T-Mobile and UScellular - **Type:** iOS setting Text-based calling for accessibility. This page explains what it does, how to use it on an iPhone and which carriers it applies to. I build **Secret Codes: IMEI & Carrier**, a free iPhone app with 317 checked codes and guides, including this one. If you would rather tap than memorise, [get Secret Codes on the App Store](https://apps.apple.com/us/app/secret-codes-imei-carrier/id6807154322). ## What is RTT and TTY? Real-Time Text sends characters as you type them during a call, so the other party reads along live. All four major US carriers support RTT, and it works with 911. TTY is the older hardware standard; iOS can emulate it in software or work with a physical TTY device over the Lightning or USB-C port. ## How do I do it? - Open the Settings app. - Tap Accessibility. - Tap RTT/TTY. - Turn on Software RTT/TTY, or connect a TTY device and choose Hardware TTY. ## Which carriers does this apply to? | Published for | any iPhone, Verizon, AT&T, T-Mobile and UScellular | | Type | iOS setting | | Good to know | RTT is supported by all four major US carriers and must be enabled per line. | _Screenshot: The Secret Codes detail screen shows the steps, the carriers and an Open in Phone button._ ## Related iphone calling features - [Auto-Answer Calls](/blog/auto-answer-calls-iphone/) - [Dial Assist](/blog/dial-assist-iphone/) - [Call Audio Routing](/blog/call-audio-routing-iphone/) - [Allow Calls During Focus](/blog/allow-calls-during-focus-iphone/) - [Announce Calls](/blog/announce-calls-iphone/) - [Wi-Fi Assist](/blog/wi-fi-assist-iphone/) See all [iphone calling features](/blog/iphone-codes/iphone-features/) or [every category of iPhone codes](/blog/iphone-codes/). ## How Secret Codes helps Secret Codes keeps this and every other entry a search away. Pick your carrier once and each entry says whether it is published for your line. You can save favourites, add a private note, and record whether a code worked on your line. **Secret Codes: IMEI & Carrier** is free on the App Store: https://apps.apple.com/us/app/secret-codes-imei-carrier/id6807154322 ## FAQ ### What is RTT and TTY on iPhone? Text-based calling for accessibility. Real-Time Text sends characters as you type them during a call, so the other party reads along live. All four major US carriers support RTT, and it works with 911. ### What else should I know about RTT and TTY? TTY is the older hardware standard; iOS can emulate it in software or work with a physical TTY device over the Lightning or USB-C port. ### What are the steps for RTT and TTY? 1. Open the Settings app. 2. Tap Accessibility. 3. Tap RTT/TTY. 4. Turn on Software RTT/TTY, or connect a TTY device and choose Hardware TTY. ### Where do I find RTT and TTY? In the Settings app on your iPhone. ### Is there a dial code for RTT and TTY? No. On iPhone this is not a dial code, so you use the steps on this page instead. ### Which carriers does RTT and TTY work on? It is published for any iPhone, Verizon, AT&T, T-Mobile and UScellular. RTT is supported by all four major US carriers and must be enabled per line. ### Does RTT and TTY work on Android phones too? These steps are for iPhone. Android phones have their own menus. ### Will RTT and TTY work outside the US? The iPhone steps stay the same, although some features depend on your carrier and region. ### What if RTT and TTY does not work on my iPhone? Check that it applies to your carrier first, because carriers decide which services they offer and can change them. If it should apply to your line, contact your carrier. ### What is related to RTT and TTY? Auto-Answer Calls. Pick up automatically after a set delay. ### What else is in this category? Dial Assist. Automatically fix country prefixes when travelling. ### Can I find RTT and TTY in an app? Yes. Secret Codes, a free iPhone app, includes it with its steps and carrier details. ## Sources - [Apple Support: iPhone User Guide](https://support.apple.com/guide/iphone/welcome/ios)