Modern smartphones from Xiaomi have long ceased to be just devices for calls, turning into powerful multimedia centers, but the function of two devices is not the same. SIM-The cards remain one of the most popular, with users often combining personal numbers with workers or connecting tariffs from different operators to save money on the mobile Internet. Owners of new devices sometimes face the need to activate a second SIM card, which by default may not be configured or disabled in the software.
The process of turning on the second line on Redmi and Poco smartphones may vary depending on the version of the MIUI operating system or the new HyperOS. It is important to understand that the physical installation of the card in the tray is only half the battle, since the software part requires the correct configuration of network settings. In this article, we will discuss in detail all the stages of activation, setting priorities and solving common problems.
It’s worth noting that some models, especially those released for the Chinese market, may have specific restrictions or require a modem switch. Two-sim mode on such devices often works stably, but requires careful attention to choosing a memory card slot if it is combined with a second sim tray.
Physical installation SIM-cardboard
Before you go to software settings, you need to make sure that the physical installation of the communication modules is correct. SIM-cards on smartphones Xiaomi is usually located on the lower or upper end of the case and is removed using a special clip coming in the kit. Modern models use a combined slot where the second SIM card shares space with the microSD memory card, so it is important not to damage the contacts when installing.
When installing, make sure that the cut-out angle of the plastic card matches the shape of the tray and the golden contacts point downwards.A little effort when pushing the tray back into the case is permissible, but it should be moderate so as not to break the locking mechanism. Once installed, the device will automatically detect a new one. SIM-The card will be offered to adjust its parameters if it has not been done before.
⚠️ Warning: Never try to remove or insert SIM-card while the phone is on, unless the Hot Replace feature is activated in the settings, this may cause damage to the reader's contacts or a software failure in the operator's definition.
If your smartphone supports eSIM, you don't need a physical installation at all. QR-This frees up one physical slot to use the memory card, which is especially true for models without expansion of memory.
☑️ Installation verification SIM
Activate the second line through MIUI settings
After you have successfully physically installed the card, you need to activate it in the software shell. To do this, go to the Settings menu, then select the section. SIM-Maps and mobile networks. In the list that opens, you'll see both cards installed; if the second card is gray or marked "Disabled," click on it and switch to active state.
You can also customize the use cases for each line in the same menu. MIUI It allows you to flexibly manage which SIM card will be used for mobile internet, voice calls by default and sending. SMS-It is recommended to immediately assign clear names to the cards, for example, "Worker" and "Personal", so as not to confuse in the future.
Particular attention should be paid to VoLTE (Voice over LTE) settings, which allow you to make calls over a 4G network without switching to 2G/3G. To activate this feature, you may need to log into an engineering menu or use a special code if the standard switch is hidden by the operator.
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If the second SIM card is not activated, try to move it to the first slot. Sometimes one of the contacts in the tray may be oxidized or slightly deformed, and changing position will help diagnose the problem.
Keep in mind that dual 4G/LTE cards are not available on all models, with one card running at high speed and the other going to 2G/3G standby, although Snapdragon and MediaTek are increasingly supporting full-fledged 4G Dual.
Setting priorities and use cases
Proper distribution of tasks between two SIM cards is key to a comfortable use of the smartphone. In the mobile network settings section, you can choose which line will be responsible for data transfer, which is especially important if one operator has a tariff with unlimited Internet, and the other has a packet of minutes for calls.
Xiaomi system offers a convenient function "Smart" SIM-A card that automatically switches the mobile internet to a card with a better signal if the main one loses connection, however, be careful with this option, as it can lead to unintended traffic consumption from a more expensive SIM card in the area of poor coverage of the main operator.
To manage calls, you can set a specific SIM card for each contact in the phone book or manually select a line before each set, allowing you to flexibly control costs and separate work and personal communications without having to constantly change the settings in the menu.
You should also consider setting up forwarding or responding to incoming calls with messages if you are busy, which are available for each line separately and can be personalized depending on which number the call is made to.
Use of the Engineering Menu for Advanced Settings
For advanced users who want to gain full control of the modem of the smartphone, an engineering menu is available, and it is logged in via the Phone application by typing special code, for example, ##4636##. Here you can force the network type, check the signal level in dBm and even reset the settings of the radio module.
In Phone Information, you can see about each SIM card, and if the second line doesn't see the network, you can try switching your preferred network type, for example, from LTE Only to NR/LTE/GSM, which often solves the problem of registering on the next generation network.
Be extremely careful when changing the parameters in the engineering menu. Incorrect setting of frequency bands can lead to complete loss of communication or unstable operation of the device.
⚠️ Warning: Changing the settings in the engineering menu can cause the RF path to malfunction. Do not change the values unless you are sure of their purpose, especially parameters related to frequencies and signal power.
Resetting the radio module via the Run Ping Test menu or switching modes can help if the second SIM card is “hung” and is not registered on the network after the phone is restarted.
Solving the Problems of Defining a Second SIM
The situation when a smartphone stops seeing a second SIM card is quite common and can be caused by both software and hardware reasons.The first step should always be to reboot the device, as this allows the system to re-interview the status of the slots and start the modem drivers.
If the reboot didn’t help, check if it’s blocked. SIM-map PIN-It is also worth trying to clear the cache of the Phone app and Google Play services, as accumulated errors in their work can interfere with the correct definition of networks.
The table below shows the main symptoms of problems and possible ways to solve them:
| Symptoms. | Possible cause | Decision-making |
|---|---|---|
| No signal on the second SIM. | Network malfunction | Change the network type in the settings or engineering menu |
| Always "Network Search." | Bad tray contact | Wipe the contacts with alcohol, check the integrity of the tray |
| SIM-map not defined | Physical injury | Replace SIM-card with the operator or check the tray |
| Sheds challenges. | The VoLTE conflict | Disable VoLTE for the second line in the settings |
What to do if the slot is damaged?
In some cases, the problem is solved only by completely resetting the network settings to factory settings, which will remove stored Wi-Fi passwords and Bluetooth settings, but often restores the correct operation of communication modules.
Dual SIM features in different regions
Global versions of MIUI Global and Chinese versions of MIUI China can handle the two SIM cards differently. Chinese versions often lack some frequency restrictions, but there may be problems supporting the ranges used by European or Russian operators.
When flashing from the Chinese version to the global version, it is important to consider that some models have hardware differences in modems. If the phone was originally intended for the Chinese market, after installing global firmware, you may have problems with determining a second SIM card or 4G operation.
Regional settings also affect the availability of features such as recording conversations or displaying the name of a caller. To fully work all functions in your region, you may need to change the region in your phone settings without flashing the device.
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Use of original accessories and SIM-Professionally carved cards reduce the risk of second line identification problems by 80%.
The impact of the Android version and shell on functionality
With the release of new versions of Android (12, 13, 14) and the HyperOS shell, the SIM management interface is changing. Google implements stricter security policies that may restrict applications from accessing data about the second SIM card, which sometimes leads to incorrect display of the balance or operator name.
In recent updates, Xiaomi has improved the switching algorithms between networks, making the transition less noticeable to the user. However, new features may conflict with the old settings, so after a major system update, it is recommended to recheck the configuration of both lines.
Developers are constantly optimizing the modem’s power consumption, as the two active lines significantly affect battery life.Enable power saving mode can limit the background activity of the second SIM card, delaying the arrival of notifications from messengers.