Teletype (TTY) in Xiaomi: purpose, configuration and features of use

Xiaomi’s modern smartphones come with many features that most users don’t even know exist, such as teletype (TTY, Text Telephone), a technology that dates back to the middle of the XX century and is still widely used in mobile devices including Redmi, POCO and Xiaomi’s flagship 13/14 series.

Teletype may seem an anachronism in the age of instant messengers and video calls, but for people with hearing or speech impairments, it remains a key communication tool for texting over the phone, and in this article we will explore what TTY is in Xiaomi, how to activate it, what modes of operation exist, and why it is still in demand.

It is important to note that Xiaomi’s teletype is not just an “old feature,” but a full-fledged system option integrated into MIUI firmware.It is supported on most of the brand’s devices, starting with Android 9 and later, and TTY settings may be required not only for people with disabilities, but also in specific professional scenarios, such as when working with outdated hardware or in conditions of poor hearing.

What is a Teletype (TTY) and why is it needed?

Teletype (TTY, Text Telephone or Teletypewriter) is a technology that allows real-time text messages to be sent over a phone line, originally designed for people with hearing or speech impairments to communicate on the phone without the need for voice conversation, and at Xiaomi, this feature is implemented at the software level and works through standard calls.

The basic principle of the TTY is to convert the typed text into audio signals that are transmitted over the telephone network and decoded at the other end of the line. To do this, both subscribers must have teletype devices. In modern smartphones, including Xiaomi, this feature is emulated software, without the need to connect a physical TTY- device.

Key scenarios of using teletype in Xiaomi:

• 🔇 Communication for people with hearing impairments is the ability to engage in dialogue through text messages instead of voice conversation.
• 📞 Communication in low-audience environments, such as noisy rooms or low-signal environments.
• 🏥 Medical and emergency services – some support services (e.g., helplines for the deaf) operate through TTY.
• 🖥️ Old hardware compatibility – connection to legacy systems where textual data transfer is required.

Despite the development of alternative technologies (such as sign language video calls or instant messengers), teletype remains relevant because of its versatility and reliability, it does not require an Internet connection and works even where modern services are not available.

How does teletype work in Xiaomi smartphones

In Xiaomi devices, teletype is implemented at the MIUI operating system level and uses standard data protocols. When the function is activated, the smartphone converts the input text into special tones (similar to how faxes do), which are transmitted over a voice channel. On the receiving side, these signals are decoded back into text.

Technically, the process looks like this:

1. The user types text on the keyboard of the smartphone.
2. The device encodes the characters into audio signals (according to the Baudot or ASCII protocol).
3. The signals are transmitted over the telephone line as a regular voice call.
4. The device at the other end of the line decodes the signals back into the text.

Xiaomi supports three main TTY modes, which can be selected in the settings:

• 📱 TTY Full — both subscribers use teletype.
• 🔊 TTY HCO (Hearing compatibility) – text is transmitted, but the subscriber’s voice is also heard.
• 🗣️ TTY VCO (Speech compatibility) – the subscriber’s voice is transmitted, but no text messages are sent.

The mode is chosen depending on the scenarios of use, for example, TTY Full is suitable for communication between two people with hearing impairments, and TTY HCO is suitable for communication if one of the subscribers wants to hear the voice of the interlocutor, but at the same time send text.

How to turn on teletype on Xiaomi: step-by-step instructions

You can activate the teletype function in Xiaomi smartphones through standard system settings. The process is almost the same for all models on MIUI 12 and later, including the Redmi Note 12, POCO X5 and Xiaomi 13 Pro.

1. Open the Settings app (the gear icon on the home screen).

2. Go to the Special Features section (some firmware may call Additional Settings → Special Features).

3. Find the item "Hearing" or "Speech" (depending on the version of MIUI).

4. Select Teletype (TTY).

5. Activate the switch and select the desired mode:

- TTY Full (full),

TTY HCO (Hearing Compatibility)

TTY VCO (speech compatibility)

After activation, a TTY icon will appear in the status bar, and when making a call, a keyboard for entering text will appear instead of a standard interface.

⚠️ Warning: Not all mobile operators support TTY- signals. Check with your ISP before using. In Russia TTY officially supports MTS, Beeline and MegaFon, but roaming may not work.

Teletype modes in Xiaomi: which to choose

The choice of TTY mode depends on how you plan to use the function. Let’s take a closer look at each of them:

For example, if you're calling a support team that works with TTY, choose TTY Full, and if you're talking to someone who can hear your voice but can't speak, TTY VCO is the right fit.

It is important to note that not all mode combinations are compatible. If you choose TTY Full and the other person is TTY HCO, the connection may not be established, in which case it is recommended to agree on the mode in advance.

💡

If you don’t make a connection when calling with TTY enabled, try switching to TTY Full mode, which is the most versatile and supported by most systems.

Xiaomi Teletype Problems and Their Solutions

Despite the ease of customization, Xiaomi users sometimes face difficulties when working with TTY. Let’s consider the typical problems and ways to fix them:

🔹 TTY is not enabled or the icon does not appear

• 📱 Make sure your model supports TTY (check in the device specifications).
• 🔄 Reboot your smartphone – sometimes the feature is activated after the reboot.
• 📋 Update MIUI to the latest version (old firmware may have bugs).

🔹 Text not transmitted or distorted

• 📶 Check the quality of the communication — TTY nuisance-sensitive.
• 🔊 Make sure that the interlocutor is also using TTY and selects a compatible mode.
• 📞 Try to call back, sometimes the problem is solved by reconnecting.

🔹 Operator does not support TTY

• 📡 Contact operator support and check the connectivity.
• 🌍 In roaming TTY can be blocked - check the fare conditions.

⚠️ Warning: On some Xiaomi models (e.g. Redmi 9A or POCO M3), the TTY function may be hidden in the engineering menu. To activate it, type ##4636## in the Phone app, then select Phone information → TTY mode.

Xiaomi Teletype Alternatives: What to Use Instead of TTY

While teletype remains an important feature, it can be replaced in some cases with more modern solutions, and consider the alternatives available on Xiaomi smartphones:

🔸 Video calls with sign language translation

Apps like Skype, Zoom, or Google Meet support sign language video, which requires an Internet connection, but better communication than TTY.

🔸 Messengers with voice messages

WhatsApp, Telegram or Mi Messages (built into MIUI) allow you to exchange text and voice messages without using the telephone network.

🔸 SMS and RCS- messages

If the operator supports RCS (for example, MTS or Beeline), you can send long messages with confirmation of delivery, which is more convenient than TTY.

🔸 Specialized applications

For people with hearing impairments, there are apps like Rogervision or Ava that convert speech into text in real time.

However, these alternatives have limitations:

• 🌐 Internet access is required (TTY operates via a cellular network).
• 💰 Some services are paid or have restrictions.
• 🔒 Not all emergency services support instant messengers.

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Teletype remains the only reliable way to text without the Internet, and alternatives are more convenient, but depend on network connectivity.

The future of teletype: will TTY remain in the new models Xiaomi

With the development of technology, the question arises: will the teletype become obsolete? Xiaomi has not yet announced the abandonment of TTY, and the feature continues to be present even in the latest flagships, such as Xiaomi 14 Ultra or POCO F6 Pro.

✅ Legislative requirements: In many countries (including the US and EU countries), support for TTY is mandatory for smartphone manufacturers to ensure connectivity for people with disabilities.

✅ Infrastructure compatibility: Many government and health services still use TTY to communicate with customers.

✅ Reliability: Unlike Internet-dependent services, TTY works even when there is no 4G/5G network or Wi-Fi.

At the same time, Xiaomi is gradually integrating more modern solutions, such as MIUI 14, which has introduced support for live subtitling (speech is converted to text in real time), which may eventually reduce dependence on TTY. However, a complete abandonment of teletype is unlikely at least in the next 5-10 years.

In the models Xiaomi 2026 (for example, Xiaomi 14T) TTY function is saved, but its settings moved to the section "Additional features" → "Special features", which can complicate the search for new users.

FAQ: Frequent questions about Xiaomi teletype