Xiaomi smartphone owners often encounter a clause in the settings that raises questions, especially if it appears suddenly or requires attention after a system update. SIM-A card is not just a list of contacts stored on a chip, but a powerful network connection management tool that allows you to fine-tune your device's interaction with the carrier. Understanding the functionality of this section is critical for the stable operation of mobile communications and the Internet.
In modern MIUI and HyperOS shells, this partition is hidden deep enough that the casual user does not violate important parameters, but its capabilities allow you to solve many problems with coverage and switching between networks. If you notice that the phone is not catching a signal or is not working correctly with two SIM cards at the same time, this is the solution. We will detail what hidden functions are available to the user and how to use them to optimize communication.
⚠️ Note: Change the settings of the preferred network type (e.g. switching to a network) 2G/3G) It can significantly reduce mobile internet speeds, but it can help extend battery life in areas with poor coverage.
What is hidden behind the concept of "Menu" SIM-map»
Under the term “menu” SIM-In the context of Xiaomi devices, users most often mean two different interfaces, the first is a standard interface for managing contacts and messages stored directly on the operator’s chip. The second, more technical, is a set of network settings that control the modes of operation of the radio module, and the second option is of greatest interest to advanced users who want to improve the quality of communication.
Within this partition, the system provides access to the logic of operator choice. The smartphone constantly scans the airwaves, and the MIUI algorithms decide which tower to connect to. Through the SIM menu, you can forcefully limit this choice, causing the phone to ignore certain frequencies or communication standards, which is sometimes necessary in roaming or in places with unstable 4G/5G signal.
In addition, identification codes are managed here. PIN-The code protects your SIM card from being used on other devices, and PUK-Ignoring the security of this partition can lead to a complete blockage of network access, so it is important to understand the difference between the unlock codes of the phone screen and the access codes of the operator chip.
What's the difference between SIM-Menu and Engineering Menu?
How to enter the settings SIM-maps and management
The path to basic SIM card settings in Redmi and Poco smartphones is standardized, but may vary slightly depending on the shell version. To access basic features such as renaming a card or setting a pin code, follow the path: Settings → SIM-Maps and mobile networks: This shows both physical cards and virtual eSIMs, if supported by the device.
For more in-depth customization, including choosing the preferred network type, the algorithm is as follows: Open Settings, go to About Phone and click on Kernel Version or Version several times. MIUI, To activate additional options if they are hidden, however, most often just go to Settings. → SIM-maps and mobile networks → (Select a SIM card) → Preferred type of network.
☑️ Checking settings SIM-map
In some regions or custom firmware, the path may look different, and if standard methods don't work, you can search by settings, type "SIM" or "Mobile Networks" into the search box, and the system will suggest the desired section, which is especially true for global firmware versions, where the menu structure can be adapted to local requirements of carriers.
Managing Contacts and Messages on a Chip
One of the classic features available through the SIM menu is the phone book. Even though modern smartphones store contacts in the Google cloud or Mi Account, the SIM card remains a universal carrier that allows you to quickly transfer numbers when you change your device without using the Internet.
It is important to remember the technical limitations of this method. SIM card has extremely small memory and a limited format of data storage. It usually allows you to save only a name and one phone number, ignoring additional numbers, email addresses, photos and addresses that may be in contact on a smartphone.
It also manages incoming SMS messages stored on the SIM card, and while modern phones default to internal memory, old messages can remain on the chip, allowing you to view them, copy them to the device's memory, or delete them to free up space, although the SMS SIM card's storage capacity is also limited and rarely exceeds a few dozen messages.
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When copying contacts from phone to SIM-The name card can be cut to 10-15 symbols due to storage format limitations, it is recommended to check the list after transfer.
Configure preferred network type and operator
One of the most important features for frequent users is manual network search. In automatic mode, the phone chooses the operator with the best signal, but sometimes it clings to a weak tower or roaming partner with an expensive tariff. In the Network Selection menu, you can turn off automatic mode and manually select an available operator from the list.
The default setting is “LTE Preferred” or “5G/LTE/3G/2G (auto).” This means that the phone will tend to catch the fastest Internet even if the signal is unstable. Switching to 3G Only or 2G Only mode can be a useful hacking technique: in places where 4G catches “one stick,” the phone constantly loses the network and searches for it again, consuming battery power. Fixing to 3G will provide a stable, albeit slow, signal.
| Type of network | Data transfer speed | Stability of coating | Impact on the battery |
|---|---|---|---|
| 2G (GPRS/EDGE) | Very low. | Maximum | Minimum |
| 3G (UMTS/HSPA) | Medium | Tall. | Average. |
| 4G (LTE) | Tall. | Medium | High. |
| 5G | Maximum | Low (in RF/CIS) | Very high. |
With two SIM cards, the setting becomes even more flexible. You can assign one card to the priority for data transfer (4G/5G), a leave the second for voice calls in mode 2G/3G. This saves energy and avoids module conflicts when both cards are trying to maintain a high-speed connection at the same time. SIM-maps where each card is selected for its use scenario.
Security: PIN, PUK and card lock
SIM card security starts with PIN-This is a personal identification number that is requested when you turn on your phone or remove your card. In the Xiaomi SIM menu, you can activate the request for this code by changing it to a more complex one or turning it off altogether (which is not recommended). Standard codes are often “0000” or “1234” and changing them is the first thing to do after buying a new SIM card.
⚠️ Note: Three times incorrectly entered PIN-The code blocks the SIM card. PUK-code that is on the plastic card-holder issued when buying a SIM card, or in the operator’s personal account.
If you forgot. PUK-If you have a code or blocked a card, it can be difficult to restore access, the phone's menu does not store these codes in the open for security reasons, if you have a lock, you need to contact the carrier. PUK through USSD-commands from a different number or through a mobile app, but a physical carrier card remains the most reliable source.
Also available in this section is the SIM card lock function. PIN-This is because it blocks outgoing calls and data use, but incoming calls can take place (depending on the operator). This is convenient if you want to leave your phone on to receive important calls, but to prohibit the use of the Internet or paid services, for example, when the phone is used by a child.
Solution: Phone can’t see SIM or no network
One of the common problems that menu settings help to cope with is when Xiaomi stops seeing the SIM card or constantly writes “No network.” Before you carry the phone to the service, you should try software solutions. The first step should always be to reboot the device, but if this did not help, move to settings.
Go to the SIM menu and try to manually change the network type. If you had 5G/LTE, switch to 3G/2G. If the network appears, then there is a problem with 4G/5G coverage in your zone or in the operator settings. Also an effective method is to reset the network settings. In addition, or through a search for settings, find the Reset option Wi-Fi, mobile networks and Bluetooth. This action will return the network settings to factory settings without deleting your personal data, photos or applications.
If the phone is writing «SIM-No card found" or "Emergency Calls Only," check if the slot on the menu is activated. In dual-symbol devices, sometimes a software failure occurs and one of the slots is disabled. SIM-Make sure the switch opposite the slot is on, also try to remove the card, wipe the contacts with a stripe or soft cloth and insert back, making sure that it sits tightly.
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If resetting network settings and manual mode switching did not help, and the phone does not see the SIM card even after rebooting, there is a high probability of a physical malfunction of the communication module or the SIM card itself.