Owners of modern smartphones Xiaomi, Redmi and Poco often face the need to use two numbers at the same time, this can be due to the separation of work and personal calls or the desire to save money by combining tariffs of different operators. However, after buying a device or resetting settings, users sometimes find that the second slot is not active or the system does not see the installed card.
The process of activating the second slot in the MIUI or HyperOS shell usually does not require complex manipulations, but has its own nuances depending on the region of the firmware. Sometimes the problem lies not in the software settings, but in the physical installation or incompatibility of the map format. In this article, we will discuss in detail all the stages of inclusion, from physical installation to fine-tuning communication priorities.
It’s worth considering that some models released for markets may have a software limitation or hybrid slot. Understanding your device’s architecture will help avoid wasting time. We’ll look at both standard action algorithms and ways to solve common definition errors.
Physical installation and tray inspection
The first and most obvious step is to verify the physical presence of the SIM-Many users forget that on some Xiaomi models, the tray can be hybrid, that is, in the second compartment you can install either a second SIM or a microSD memory card. If there is a memory card in the slot, then the second number will not work.
To remove the tray, use a special paper clip included in the kit or a thin needle. The extraction hole is usually located on the lower or upper end of the case. It is important to insert the tool perpendicularly and with moderate effort so as not to damage the mechanism. After extracting, carefully examine the contacts on the map and in the slot itself for contamination.
⚠️ Warning: Never try to insert SIM-The card is in a phone turned off if possible, but it is strictly forbidden to insert or remove the card while the phone is on, without support for the Hot-swap feature (although modern Android allows this, the risk of static discharge or failure of the power controller remains). It is better to carry out the procedure with the device turned off.
Note the size of the card. Modern smartphones use Nano-SIM. If your card is old format (Mini or Micro), you either have to replace it from the operator or gently cut it along the contour, although the latter option is less reliable. Wrong size can lead to a tray getting stuck inside the case.
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Use the original paperclip from the kit.Third-party tools can have a tip too thick and damage the tray extraction mechanism, which will require disassembling the phone for repair.
After installing the map and returning the tray to the case, turn the device on. SIM-map and run the setup wizard. If that doesn't happen, go to software activation via the settings menu.
Activation through the system settings menu
If the card is physically set correctly, but there is no connection, you need to check the software switch. MIUI and HyperOS SIM card management is in a separate section. Go to Settings, then select SIM-maps and mobile networks. This shows all the maps installed.
In the menu that opens, you'll see a list of slots. They're usually signed as SIM 1 and SIM 2. Each slot should have a switch next to it. If it's turned off (gray), the system ignores the card. Put the slider in the active position. Then the signal level should appear next to the operator's name.
☑️ Verification of activation SIM
Sometimes the system suggests selecting the network type for each card separately. 4G/LTE or 5G, If it is supported by your tariff and coverage in the region, be sure to activate data transmission if you plan to use the Internet from the second SIM.
| Parameter | Description | Recommended value |
|---|---|---|
| SIM on. | The main slot switch | Actively. |
| Type of network | Communication standard | Preferably LTE/5G |
| Data roaming | Transfer of data abroad | Off (default) |
| Name of the network | Displayed name | Personal/Worker |
In the same menu, you can set profile names to keep your calls from getting confused, like "Main" and "Internet," which will make navigation easier later, and after settings are applied, the phone may need to reboot to initialize the communication module.
Setting Challenge Priorities and the Internet
Once both cards are successfully activated, the user is faced with the issue of traffic and call management. Android allows you to flexibly configure which SIM will be used by default for various actions. This is critically important so that you do not waste expensive traffic of the main card or call from the number that ran out of minutes.
In the section SIM-maps and mobile networks, find the default block. Here you can select a map for voice calls, SMS You can set up a permanent choice or leave the "Always Ask" option, which is convenient if you rarely use a second SIM for calls.
The smart switch feature deserves special attention. In some versions of the firmware, an option is available that allows you to use the Internet from the main one. SIM-cards even while talking on the second, if the second does not support VoLTE. However, for stable operation, it is better that both cards support VoLTE technology.
To set up the Internet, click on "Mobile Internet" and select the card you want, and the system will warn that the second card may become unavailable for data transfer or go into 2G/3G mode during a call if the device does not support Dual 4G Standby mode, which is normal behavior for many budget models.
Solving problems with the definition of the second SIM
It's not common for a phone to see one card but ignore the other, but it does. Often it's a software failure of the radio or a contact group that's damaged. First of all, try restarting the device in safe mode to eliminate the impact of third-party apps.
If the reboot didn’t work, check the IMEI. Dial the code *#06#. The window that appears should show two IMEIs corresponding to both slots. If the second IMEI displays “Null”, “000000000” or the field is empty, this indicates a serious problem with the modem or hardware firmware.
⚠️ Attention: If IMEI The second SIM is missing or is displayed incorrectly, do not try to reflash the modem yourself without special knowledge. This can lead to a complete loss of the ability to make calls (brick for communication.
The problem may also be in the SIM-If the problem has moved to the first slot, the operator's card is not working, if the second slot has stopped seeing any card, the contacts inside the phone may have oxidized or the antenna module's plume has failed.
Hidden settings of the engineering menu
Dual SIM and 4G/5G
The technology of two SIM cards simultaneously has its limitations, depending on the hardware platform of the smartphone. Most modern Qualcomm and MediaTek processors support Dual 4G mode, but with reservations. Usually only one card can work in high-speed 4G/5G mode, while the second one switches to 2G or 3G for waiting for calls.
This means that if you prioritize the Internet on SIM 1, then SIM 2 can display an "H+" or "E" icon. This is not a malfunction, but a feature of the architecture. When you call a second SIM, the Internet on the first one can briefly interrupt or switch if VoLTE is not activated.
VoLTE (Voice over LTE) technology allows voice to be transmitted as a data stream without lowering the communication standard. Make sure this feature is enabled in the settings of each SIM card and is supported by your operator. Without VoLTE, simultaneous voice and data on two SIMs is not possible on most mid-range and low-end devices.
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For the stable operation of two sims, it is critical that both cards support VoLTE and this feature is activated in the operator and in the phone settings.