Teletype in the phone Xiaomi Poco: the full guide

Poco and Xiaomi smartphone owners sometimes encounter a vague icon or setting called “Teletype,” a term that sounds like an anachronism from the past, as it is associated with bulky typewriters from the beginning. XX However, in the context of the Android operating system and shells. MIUI HyperOS is a very relevant, although rarely used function.

The technology is about the ability to send text messages through a voice channel, which has historically been designed for people with hearing or speech impairments. In today's world, having an active teletype mode can cause crashes in standard calls or simply take up space in the interface. Understanding how this protocol works will help you set up your phone correctly and avoid unnecessary questions from the system.

In this article, we will look in detail at why this mode is needed in 2026-2026, where to find it in the menu of Xiaomi Poco and whether it should be touched at all by the average user, you will learn how this feature affects the quality of communication and why it is hidden or disabled by default on most devices.

Historical background and modern application

Teletypewriter (TTY) technology, or teletype, dates back to the early days of digital smartphones, which originally allowed text messages to be sent over phone lines using tonal signals. In the age of button phones, this feature has been a lifeline for hearing-impaired people, allowing them to communicate without having to hear their interlocutor. Poco and Xiaomi have implemented software emulation of this protocol.

With instant messengers and video, classic teletype seems a relic, but mobile standards still support this mode for accessibility. Operators are required to provide TTY for people with disabilities, so Xiaomi engineers are embedding this module in the firmware of global versions of smartphones.

It's important to understand that activating this mode changes the way the audio signal is processed. The phone starts encoding the text into sound tone sequences that are transmitted to the interlocutor or received from a special device at the other end of the line. For the average user who does not have specialized equipment, the mode on may be useless.

⚠️ Note: Using teletype mode without connected equipment or adapter may result in you not hearing the other person during the call, as the audio channel will be busy transmitting text signals.

Despite its archaic nature, the feature remains part of the GSM and VoLTE standards, and is on your Poco menu for compatibility and compliance with the legal regulations of different countries rather than for daily use. If you don’t use special headsets for the deaf, you probably won’t need this feature.

Where to find teletype settings in MIUI and HyperOS

Finding teletype settings in MIUI shells and the new HyperOS may not be obvious, as developers often hide this item deep in the menu.The location of the option depends on the Android version and the specific model of your Poco. Most often the path lies through the standard Phone application or general system settings.

The first way to find the feature is through the call menu. Open the app you use for calls (usually Google Phone or the standard MIUI Dialer). Click three dots in the corner of the screen and select Settings. Next, look for Accounts or Special Features, where Teletype Mode may be hiding.

The second option is system settings. Go to Settings. → SIM-Maps and mobile networks. Select your active SIM card. In the list of additional options, sometimes there is an option «TTY-If you don’t see this item, your firmware version may be hiding it by default and you’ll need to use an engineering menu or code to access it.

Analysis of TTY operating modes

If you do get to the settings, you'll see a few different ways that the protocol works, and you'll have to sort them out so you don't accidentally pick the wrong mode that will block the normal communication, and it offers flexible data streaming.

There are four main states in which your Xiaomi communication module can be located: the choice of a specific mode is dictated by the presence of special equipment on you and your interlocutor, the wrong choice will either not take place or will pass without sound.

• 📴 TTY Off: off. It's the standard state for 99 percent of users. Voice is transmitted as normal sound, text messages are not encoded into tone signals.
• 📝 TTY Full mode. The phone only works like a typewriter. You can't hear the voice of the person you're talking to, you can't talk to them, you only exchange text through special devices.
• 🔊 TTY HCO (Hearing Carry Over: A mode for those who can speak but can't hear, where you hear the voice of the person you're talking to (or text on the screen) and you respond with printed text.
• 🎤 TTY VCO (Voice Carry Over: a mode for those who hear but cannot speak. You speak with your voice, and the response from the person you are talking to comes in text.

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For normal smartphone use without special medical adapters, the only correct choice is TTY Off mode.

Switching between these modes is instantaneous, but requires a reboot of the Phone app or even the device itself to take effect.If you accidentally activate TTY Full, you might think the phone speaker broke, when in fact it just put it in text data standby mode.

Teletype Impact on Communication Quality and Battery

Many users are wondering: does the presence of this feature affect the autonomy of Poco? The software module itself, even if it is just hanging in the background in a switched-off state, consumes minimal amount of resources.

When the teletype mode is turned on, the digital-to-analog converter begins to work differently, prioritizing the transmission of tonal frequencies characteristic of the system. TTY-This can lead to artifacts in normal sound if the mode is on wrongly, and you may notice that the voice of the interlocutor sounds deaf, intermittent, or accompanied by a strange hiss.

As for the battery, there is no direct connection between active TTY and fast discharge unless there is an active call. But during a conversation, the processor gets an additional load of encoding/decoding signals. On modern Snapdragon processors, which are equipped with Poco phones, this load is invisible, but on older models it can cause the housing to heat up.

Also worth noting is the impact of VoLTE (Voice over LTE) on performance: In some rare cases, turning on TTY can conflict with 4G voice protocols, forcing the phone to switch to 3G or 2G to ensure compatibility with legacy networks, which in turn will already have a noticeable impact on Internet speed during a conversation.

How to turn off teletype on Xiaomi Poco

If you find that the feature is active, and you want to get the phone back to its standard state, you need to do a few simple things: the shutdown procedure doesn't require root rights or complex software. It's done through a standard interface.

First, make sure you're in the SIM card settings menu. As mentioned earlier, the path may be different, but the logic is the same. Find the option for availability modes or special telephony capabilities. In some versions of MIUI, it may simply be called "TTY mode."

Once you select the TTY Off value, the system may ask you to confirm the action or automatically apply the settings. In some cases, especially on older versions of Android, you need to reboot the device. If after rebooting the TTY icon in the status bar is gone, then the function is successfully deactivated.

⚠️ Note: If the Teletype Mode menu item is missing or inactive (shaded in grey), it means that your carrier does not support this feature or it is blocked at the region firmware level.

In situations where software can’t disable the function (for example, it turns on itself after resetting), you can try using the command via the engineering menu. Enter the code ##4636## in the dialer (does not work on all models). Go to Phone Information. Find the field associated with TTY and change its value to 0 or Off.

adb shell settings put global tty_mode 0

This command, executed via ADB (Android Debug Bridge) from a computer, is guaranteed to disable teletype at the system level, even if the Xiaomi shell interface is buggy, you need to connect the phone to a PC, enable debugging over USB and run a line of code in the terminal.

Problems and solutions

Despite the simplicity of the function, Poco users sometimes face problems, the most common being the inability to make a call. The phone dials, the horns go, but there is no connection. Often this is due to the fact that in the background, the conflicting TTY mode is activated, which tries to establish a text connection instead of a voice one.

The other problem is that the sound disappears, you pick up the phone, you see the timer, but you don't hear it, and it's a classic TTY Full feature, where the microphone and speaker lock in to transmit the tone, and the solution is to change the availability settings as soon as possible.

There are also cases where the TTY icon sticks in the notification curtain. Even after the function is turned off, the icon remains. This is a software bug of the MIUI shell. Helps clear the cache of the Phone application or force the process to stop through Settings → Apps → All applications → Phone → Memory → Clear.

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If the badge TTY It's gone, but there's still some sound problems, so check if the Bluetooth headset is connected. TTY-device.

In rare cases, the problem lies on the operator's side. Some SIM cards have a profile in which the teletype service is activated forcibly. If nothing helps, contact your operator's support team to request that you turn off the Teletype service on your number.

FAQ: Frequently Asked Questions