SIM card is the abbreviation of Subscriber Identity Module (Subscriber Identity Module), also known as user identification card, smart card, GSM digital mobile phone must be installed with this card to use. It stores digital mobile phone customer's information, encrypted key and user's phone book on a computer chip, which can be used to authenticate the customer's identity and encrypt the customer's voice information during the call. Pr phone cards also fall into this category.
Introduction to SIM card types:
There are four types of SIM cards:
Standard SIM (original card),
Mini SIM (also known as the standard card),
Micro SIM (small card),
Nano SIM (starting with iPhone 5, currently available only on iphones)
Main functions of SIM card:
1. Store user data
2. Operation and management of user PIN (the PIN code can be changed freely by users, which is the personal password of SIM card)
3. User identity authentication
Here mainly introduces the types of SIM cards used by Xiaomi mobile phones:
The Mi 1 series, Mi 2 series, Redmi series (excluding Redmi 4G) and Redmi Note series phones all come with a Mini SIM card, which is a standard card.
The redmi 4G mobile version and the redmi Note4G version have a small card slot on the back of the phone, which prevents large cards from being used.
Mi mobile phone 3 standard with the cato for the standard cato, at the same time for the convenience of users to provide a small card and super small cato accessories; unlike the Mi 3 series, the Mi 4 comes with a standard catto, while the standard card must be cut or replaced.
Daily maintenance of SIM
1. Oxide layer problem
The SIM card will produce oxide layer after being used for a period of time, which will affect the contact surface between the mobile phone and the SIM card. It is recommended to remove the SIM card for inspection every three months.
2. The mobile phone is incompatible with the SIM card.
The SIM card doesn't work after you get a new phone? In fact, it is because the mobile phone and SIM card are not compatible. It is recommended to find a communication operator to replace a new SIM card.