Owners of Xiaomi and Redmi smartphones often encounter obscure abbreviations in the system settings, one of which is Teletype or TTY. When you accidentally turn on this feature or find an icon in the status bar, the user has a natural question about what this mode is and how it affects the operation of the device, in fact, it is an outdated but still maintained communication standard designed for people with hearing or speech impairments.
Modern smartphones retain many legacy features to ensure compatibility with equipment of the past and comply with the laws of some countries. In the context of the Android shell MIUI or HyperOS, the management of this mode is hidden in the depths of the menu, which sometimes leads to confusion. TTY completely blocks the standard voice channel, turning the phone into a text terminal. If you do not plan to use special equipment for the deaf, active mode can cause serious inconvenience on ordinary calls.
Next, we will take a closer look at the history of the technology, how it works in today’s environment, and provide step-by-step instructions on how to manage this option on Xiaomi devices. Understanding the purpose of Teletype will help you avoid accidental communication failures and properly configure the communication capabilities of your gadget.
Historical background and purpose of TTY technology
abbreviation TTY It comes from the Teletypewriter, which translates to teletype or teletype, and it was originally an electromechanical machine, like a typewriter, that allowed text messages to be sent over telephone lines. XX This technology has become a lifesaver for people with hearing and speech impairments, allowing them to communicate at a distance without the need to hear the voice of the interlocutor.
With the advent of mobile phones and smartphones, physical connectivity of bulky hardware became impossible, but the need for function remained: Engineers integrated the TTY protocol directly into the software of mobile operating systems, including Android. Now, to use the function, you do not need an external modem, just connect a compatible adapter through the charging connector or use embedded software solutions.
Xiaomi owners may notice that there are several modes of operation, and each of them has its own characteristics of data transfer. Standard voice calls in this mode are impossible, since the channel is busy transmitting text packets. This is important to consider, so as not to miss an important call, thinking that the network simply does not catch.
- 📞 TTY Off – completely off, the phone is running in standard voice mode.
- 📝 TTY Full – the device can only send and receive text messages via teletype, voice communication is not available.
- 🗣️ TTY HCO (Hearing Carry Over – allows you to hear the voice of the interlocutor, but respond with text, which is convenient for the hearing impaired.
- 👂 TTY VCO (Voice Carry Over – the user speaks in voice but receives a text response, useful for people with speech impairments.
⚠️ Note: If you accidentally activate the mode TTY Full, you won't be able to make regular voice calls. Subscribers will hear horns, but the connection won't happen as the phone tries to establish a text session.
The principle of teletype in modern smartphones
In modern devices of the line of Redmi and Poco implementation TTY And when the function is activated, the operating system redirects the audio stream to the text decoder. TTY-adapter, then the sound signals (tonal codes) are converted into text on the screen of the device of the interlocutor, and vice versa.
The data transfer process requires a stable connection and a voice channel, which means that while using Teletype, it is impossible to start recording a conversation through standard means or use some VoIP services that conflict with telephony.
For ordinary users who do not have special equipment, activating this mode is pointless and even harmful.The smartphone will try handshake with the network as a terminal device, which in some rare cases can lead to problems with registration in the operator’s network, especially when roaming.
Technical details of the protocol
It is worth noting that with the development of video and instant messenger technologies, the need for classic TTY is decreasing, but manufacturers such as Xiaomi are required to keep this feature in firmware to meet international accessibility standards (ADA in the US and analogues in other countries).
How to turn Teletype on Xiaomi and Redmi
Control of Teletype function in the shell MIUI The interface may vary slightly depending on the Android version and regional firmware, but the logic remains the same. SIM-card.
To access the settings, you need to go along the way: Settings → SIM-maps and mobile networks → Choice SIM-cards (for calls) → Teletype (TTY). In some versions of the menu, the item may be simply called Teletype Mode or be in the Special Features section, although in modern Xiaomi it is rigidly tied to the telephony module.
☑️ Check before changing the settings
Once you log in to the TTY menu, you will be prompted to select one of the modes described above. To return to normal, you must select Off or TTY Off. Changes take effect instantly, device reboot is not usually required, but the icon in the status bar can disappear with a delay of a few seconds.
If you can't find this item on the menu, your carrier may have blocked this feature at the network level, or it's hidden in the engineering menu, in which case use the search bar in your phone settings by typing "TTY" or "Teletype".
| Mode of work | Incoming sound | Outgoing sound | Recommendation |
|---|---|---|---|
| Off (Off) | Voice. | Voice. | Standard for all users |
| Full (Full) | Text | Text | Only for deaf-mutes with an adapter |
| HCO | Voice. | Text | For the hearing-impaired |
| VCO | Text | Voice. | For people with speech impairments |
⚠️ Warning: After switching Teletype mode, a short-term network connection break may occur. 4G/LTE fall away 10-15 Seconds, the phone is re-registered on the network with new parameters.
The effect of TTY on communication quality and battery
Many users are wondering if active Teletype affects battery discharge speed. In theory, the mode of continuous data transfer and processing of text packets may consume a little more power than the standby mode, but in terms of daytime the difference will be minimal and imperceptible against the background of screen and applications.
More significant is the impact on overall communication quality. As mentioned earlier, turning on TTY changes the way the signal is encoded. In areas of uncertain reception, this can lead to the phone losing network more often or not being able to register at all, since channel stability requirements for data transmission are stricter than for intermittent voice traffic.
There are also software conflicts. Some applications for recording calls or determining numbers may not work properly if the system is busy emulating a teletype, you may notice that the call log is filled with strange entries or the duration of the conversation is displayed incorrectly.
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If you notice the phone discharges quickly or warms up during a conversation, check if Teletype mode or USB debugging is accidentally activated.
Alternatives and modern solutions for accessibility
While TTY is the de facto standard for emergency services in many countries, Xiaomi and Redmi users have more modern tools for everyday communication.The Android ecosystem offers a wide range of Special features that work more efficiently and require no special hardware.
For example, Google’s Live Transcribe feature, which is pre-installed on many Xiaomi smartphones, allows you to translate your voice into text in real time with high accuracy, which solves the problem of hearing impaired people without having to switch the phone to the archaic Teletype mode.
- 🔊 Sound amplification – software volume increase above hardware constraints.
- 🎨 Visual Notifications – Camera flash when incoming call for deaf.
- 🗣️ Voice access – full control of the smartphone voice without touching.
Using video messengers also allows you to use sign language, which is impossible in the classic TTY mode. Therefore, for most users, disabling the teletype is the optimal solution, freeing up the system resources.
Frequent problems and ways to solve them
Sometimes users are faced with a situation where the TTY icon in the status bar is constantly burning, even if they did not turn on this feature, this can be due to a malfunction of the system application Phone or a conflict with installed applications for calls.
To solve the problem, try clearing the cache of the Phone app. To do this, go to Settings → Apps → All Apps → Phone → Memory → Clear the cache. This action is safe and will not delete your contacts or call history, but reset the temporary settings of the communication module.
In rare cases, especially on custom firmware, the Teletype menu may be hidden, and in such a situation, you can try to activate the hidden menu through the engineering code by typing the command ##4636## into the dialer. However, this should be done with caution, since changing the parameters in the engineering menu can lead to loss of signal.
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The main purpose of TTY is to make communication available to people with disabilities, and for the average user, the best and only true setting is to completely disable this feature.
⚠️ Note: Do not try to use third-party apps from the Play Market for emulation TTY, If you're not sure about their safety, they may be asking for excessive permissions to access the microphone and contacts.