Second Sim on Xiaomi: selection, configuration and modes of operation

Owners of modern Xiaomi smartphones often face the need to use two or more phone numbers at the same time, this may be due to the separation of personal and work contacts, the use of advantageous tariffs of different operators or the need to roam without changing the main card. However, despite the presence of two slots, the process of choosing an active line for a particular call or message can cause questions for users, especially after updating the MIUI or HyperOS interface.

The Android system installed on Xiaomi devices provides flexible communication management tools that go far beyond simple slider switching. Smart switching between SIM cards allows you to automate the process of outgoing calls, saving time and preventing accidental spending of funds from inappropriate tariffs. Understanding the logic of these settings is critical for comfortable operation of the gadget.

In this article, we will discuss in detail how to properly configure the second SIM, what are the nuances of working in 4G and 5G networks, as well as how to avoid typical errors that lead to missed calls or the inability to access the Internet. When installing two SIM cards of the same operator (for example, MTS and MTS), the system can automatically assign them different names, which requires manual verification to avoid confusion when choosing a number.

Physical installation and primary activation of slots

Before you go to software settings, you need to make sure that the correct physical installation of communication modules. the tray for SIM cards in Xiaomi smartphones is usually located on the lower or lateral end of the case and is removed using a special clip.

Once the device is turned on, the system automatically recognizes the new modules. A notification will appear on the screen asking the user to configure the cards that have just been installed. At this stage, the user is asked to assign each of them a label, for example, "Main" or "Additional", and also select a color indication for visual distinction in the dialing interface. Slots are identified by their physical location, but in the software shell they can be logically reassigned.

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If the second SIM card is not identified, try to wipe the contacts on the card itself and in the slot with dry soft cloth, and also make sure that the card is trimmed according to the Nano-SIM standard without damaging the chip.

It is worth noting that at the first start the phone can request PIN-If the code was installed on the card, entering the wrong code several times in a row will lead to the blocking of the SIM card and the request. PUK-Once successfully unlocked, both lines are given the status of "Active", as evidenced by the appearance of appropriate icons in the notification curtain.

Basic setting of call priorities and the Internet

The main control of communication parameters is concentrated in the settings menu. To get there, the user needs to open the Settings app and find the SIM card and mobile network section, and this is where the roles are distributed among the installed modules. The system allows you to set the default card for voice calls, SMS-messaging and mobile internet.

There are three basic ways to make calls: One is to fix the card rigidly, where all outgoing calls always go through the slot chosen; the other is to always ask, which causes the phone to display a dialog box with a number selected before each set; the third option, often called Smart Choice, allows the system to offer the last number or number that the caller was last called from.

• 📱 Card 1: The main number for business correspondence and important calls.
• 🌐 Map 2: tariff with a large pack of traffic for navigation and instant messengers.
• 💬 Hybrid mode: the ability to select a SIM directly in the dialing interface before calling.

Mobile Internet settings deserve special attention. Unlike calls, 4G/LTE network access can only be active on one SIM card at a particular time. Switching the APN access point between slots is automatic, but it can take several seconds during which communication is interrupted. Therefore, it is recommended to assign a card with better coverage or unlimited tariff for the main data transfer.

4G Dual SIM Mode and Its Impact on Communication

One of the key functions in Xiaomi smartphones is support for Dual SIM 4G technology. In older phones with active use of the Internet on one SIM card, the second automatically switched to 2G/3G mode, which could lead to a deterioration in the quality of voice communication or the inability to receive a call if the reception area was not covered by second and third generation networks.

The technology allows both slots to be on fourth-generation networks at the same time, which means that while you download files via LTE on the first card, the second one remains available for incoming calls in high quality. However, it is worth considering that if you actively use the data channel on one SIM card, the Internet speed on the second one can be limited or the connection will be suspended until the session is over.

To activate this feature, you need to go to the SIM card and mobile network menu and find the "Use 4G for the second SIM card" switch. Once this option is enabled, the system will reconnect both modules to LTE networks. If the operator of the second card does not support voice calls over LTE (VoLTE technology), then during a conversation the phone can temporarily switch to 3G, which is normal behavior.

Configure contact names and color indication

Visual SIM card differentiation is an important aspect of ergonomics that users often ignore, and Xiaomi’s dialing interface has the ability to display numbers or contact names in different colors depending on which SIM card they are planning to call from, helping to avoid awkward situations where an important call is not coming from the number they were originally planning to call.

To adjust the color schemes, go to the Phone app, click three dots in the corner of the screen and select Settings, then "Additional" or "Call settings" immediately. Here you can assign a specific color for the first and second SIM card, such as blue for work and green for personal affairs, these colors will be displayed on the call button and in the call log.

In addition, each SIM card can be given a clear name, and instead of the standard "SIM 1" and "SIM 2", the system allows you to enter "Worker", "Home", "Travel" or carrier names, these names will appear in the notification curtain when choosing a network for a call, personalization helps you navigate your settings faster, especially if you have cards on the phone from different carriers.

Solving switching problems and communication quality

Despite the fact that the software is fine, users may experience situations where the second SIM card stops responding, the network disappears or calls do not pass. Often the cause is a software failure in the communication module. In such cases, the effective method is to reset the network settings, this action will not delete personal data, photos or applications, but return the connection parameters to factory values.

You can reset via the Settings menu → Connection and Sharing → Reset Wi-Fi, mobile networks and Bluetooth. Once the phone is rebooted, you will need to re-enter passwords from Wi-Fi networks, but the SIM card configuration will clear out possible errors. It is also worth checking whether the Flight mode for a particular slot is activated in quick settings.

⚠️ Warning: If the second SIM card is still undetected after resetting, try swapping slots in places.This will help to identify a malfunction of a particular connector in the phone or damage to contacts on the SIM card itself.

Another common problem is that some virtual communication operators (MVNOs) cannot run 4G simultaneously on both cards, in which case the phone can force the second card to 2G. The solution lies in manually configuring network types: the network selection menu for the problem slot should uncheck the “LTE Preferably” box and leave only 3G/2G to stabilize the connection.

Table of comparison of modes of operation of SIM cards

To organize information about the different modes of operation of two SIM cards on Xiaomi devices, you should read a comparative table, which will help you choose the optimal configuration depending on your needs.

And you can see from the table that the 4G Dual SIM mode is the most functional, but also the most power-hungry. If you're in a hot spot, the phone will spend a lot of battery life constantly searching for and holding the signal for two slots at once, and in such situations, it's wise to temporarily turn off the second SIM card or put it into call-only mode.

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Optimal configuration for most users: the main SIM with unlimited Internet is configured for data transfer, and the second (with a package of minutes) is only for voice calls, which balances the load on the battery.

Use of VoLTE and Wi-Fi Calling

Current communication standards allow high-quality voice transmission over an LTE network, which is known as VoLTE (Voice over LTE) technology. On Xiaomi smartphones, this feature is often turned on by default, but it requires support from the operator and a tariff plan. With active VoLTE, voice is transmitted as a data stream, which allows you to simultaneously talk and use fast Internet without switching to 3G.

Another useful option is Wi-Fi Calling, which allows you to make and receive calls over a Wi-Fi network in places where mobile communication is absent or extremely weak (for example, in basements or outside the city), to activate you need to go to the SIM card settings and turn on the appropriate switch, the sound quality in this case depends on the speed of your Internet connection.

⚠️ Note: When using Wi-Fi Calling, make sure that the settings indicate which calls are preferable: over a mobile network or Wi-Fi. Incorrect settings can cause the phone to try to call over Wi-Fi even when its signal is weak, ignoring a stable mobile network.

Customizing these features is especially relevant for the second SIM card, which is often used as a backup card. If the main card is busy talking or giving out the Internet, having an active VoLTE on the second line ensures that you do not miss an important call and the quality of communication remains at a high level.

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