how to lock sim card

   There are a lot of people asking how to unlock the SIM card,but few people ask "How to lock sim card?".

   How to lock sim card?Before answering this question, let's get to know a few questions about the SIM card.

   What is the sim card？SIM is the abbreviation of the customer identification module card, also known as the user identification card, smart card, GSM digital mobile phone must be installed on the card, so that we can use it.On the computer chip to store the information of customers, encryption keys and user's phone book and other content,which can be used to identify the identity of the GSM network,and it will encrypt the voice of the customer. 

   How to lock sim card?What is the principle of SIM card?

   SIM card is a chip with a microprocessor,

Within 5 modules, each module corresponds to a function:

CPU (8 bit /32 bit /16 bit), program memory ROM, working memory RAM, data memory EEPROM and serial communication unit, these 5 modules are integrated in one integrated circuit. When the SIM card is connected to a mobile phone, a minimum of 5 connecting lines are required:

* power (Vcc) * clock (CLK) * data I/O (Data) * reset (RST) * ground terminal (GND).

   How to lock sim card?What is PIN code?

   PIN code refers to the password of SIM card , exists in the SIM card, the factory value is 1234 or 0000.After the activation of the PIN code,every time we want to start, we have to enter the PIN code to log on the network.PUK code is used to solve the universal key PIN code, it is a total of 8. Users are not aware of the PUK code, only to the operating room by the staff to operate.

   How to lock sim card?When the PIN code is lost 3 times, the SIM card will automatically lock,at this point, we only have to enter the PUK to unlock.PUK code altogether has 10 times to enter the opportunity. At this time, users don't go to touch the PUK password, the wrong 10 times, SIM card will automatically start the self destruct program, the SIM card failure. At this point, only to re open the business hall for cards. In fact, as long as careful use,the password of PIN will only protect your security.