The SIM card (user identification module) is also known as smart card, user identification card, GSM mobile phone must be equipped with this card to use. The system can reliably ensure the normal communication of users and prevent the eavesdropping of parallel computer and telephone. At the same time, China Unicom and China Mobile also issue SIM cards to mobile phone users. SIM card is also widely used in bank POS terminal. So the corresponding SIM card has also been a great development.

SD card is a storage device based on semiconductor flash memory technology. Due to the small size, light weight, large storage capacity, fast data transmission speed, flexible movement, data security, complete structure, no need to worry about the damage of mechanical movement. Suitable for mobile phone, MP3 player, Walkman, digital camera, digital camera, portable computer and other devices. The cardholders corresponding to SD card have also been developed greatly, and the cardholders of SD card and SIM card have to meet the requirements of SIM card, SD card, system connection and information exchange. According to the needs, enterprises should formulate product standards, how much is the SIM card holder, and manage the holders of SIM card and SD card.

When it comes to SIM cards, the first thing we want to talk about is SIM cards. It's a plug-in that matches the SIM card. The SIM card fixing device contacts with the SIM card through the spring plate on the SIM card fixing device. The SIM card holder is used in a mobile phone to provide an interface between the mobile phone and the SIM card. The function and sequence of the socket are the same as that of the SIM card.

SIM card is also called smart card and user identification card. Digital mobile phones must be equipped with smart card connector to use this card. The SIM card consists of five modules, each module has one function: microprocessor CPU (8 bits), program memory ROM (3-8kbit), working memory RAM (6-16kbit), data memory EEPROM (128-256kbit) and serial communication unit. The SIM card interface terminal is connected with the circuit terminal, which includes clock card, reset card, power card, data card, programming terminal and grounding terminal. The power supply of the SIM card is 5V, 5V and 3V compatible, 3V and 1.8V. At present, both Microsim and nanosim cards are 1.8V. The SIM card generated by the mobile phone needs to provide the power supply voltage matching with the SIM card. After the smart card connector is inserted into the SIM card of the mobile phone, the power port supplies power to the module in the SIM card.