There are two types of mobile phone cards: 1. Embedded SIM card, commonly known as small card. The size of this card is only "25mm×15mm" and is a card that is semi-permanently installed in a GSM mobile phone; 2. , Card-type SIM card, commonly known as large card, the size of this card is "54mm × 84mm", large card complies with the ISO7816 standard for IC cards, similar to IC cards, users can use the card by inserting it into a mobile device.
The operating environment of this tutorial: Windows 7 system, Dell G3 computer.
How many types of mobile phone cards are there?
Mobile phone cards generally refer to SIM cards.
SIM (Subscriber Identity Module) card is an IC card held by mobile users of the GSM system, called a subscriber identification card. The GSM system identifies GSM users through SIM cards. The same SIM card can be used on different mobile phones. GSM mobile phones can only be used online after inserting a SIM card.
The SIM card is the key for GSM mobile phones to connect to the GSM network. Once the SIM card is pulled out from the mobile phone, the mobile phone will not be able to enjoy various services provided by the network operator except for emergency calls. In addition to being used as keys, SIM cards also provide users with a lot of convenience. Users only need to insert or embed the SIM card into any GSM terminal to achieve communication. The SIM card also manages a lot of information provided to the user's services and can be used to store short messages, especially those received when the user does not turn on the phone or is away.
1. Structure of SIM card
The SIM card is a smart card containing a microprocessor. It consists of CPU (8 bits), RAM (working memory, 6~16kB ), ROM (program memory, 3~8 kB), EPROM or EEPROM (data memory, 128~256 kB) and serial communication unit. These five modules are integrated into an integrated circuit to prevent illegal Access and theft, because the connection between the chips may become an important clue to illegal access and theft of the SIM card.
When the SIM card is connected to the mobile phone, at least 5 connections are required, as shown in Figure 1. In the figure, Vcc is the power supply, CLK is the clock, Reset is reset, N.C is unused, Gnd is the ground terminal, I/O is the data input and output interface, and Vpp is the programming voltage. Whenever the phone is turned on, the mobile phone must communicate with the SIM card. Some data signals can be measured on the SIM card holder with an oscilloscope.
2. Types of SIM cards
There are two types of SIM cards in actual use with the same function but different appearances:
①Embedded SIM Card (commonly known as small card): This card is only 25mm × 15mm in size (smaller than an ordinary stamp) and is semi-permanently installed in a GSM mobile phone. It is currently the most popular SIM card. If you want to change a small SIM card into a large SIM card, you only need to buy a SIM card holder, and the small SIM card can be used as a large SIM card.
②Card-type SIM card (commonly known as blockbuster): The size of this card is 54mm×84mm (about the size of a business card). The big card complies with the ISO7816 standard for IC cards. Similar to IC card. Users can use the card by inserting it into their mobile device.
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