Card reader is a common data transmission device used to read the information in the storage media, and the communication module is one of the core components of the card reader, which is responsible for the transmission and interaction of data. The main function of the communication module is to connect the card reader to other devices (such as computers, mobile devices or terminals). According to different application scenarios, the communication module can support a variety of communication interfaces, such as USB, serial port (RS232/RS485), Ethernet, Wi-Fi, Bluetooth, and NFC. These interfaces not only determine the speed of data transmission, but also affect the compatibility and use scenarios of the device. In the technical realization, the communication module usually includes the control chip, the signal converter and the related software protocol stack. The control chip handles the sending and receiving of data, and the signal converter is used to match signals between different communication standards. Taking NFC as an example, its communication module can realize short-distance and high-speed data transmission, which is very suitable for mobile payment and access control scenarios; Ethernet-enabled modules provide a stable network connection for monitoring systems or industrial automation. In general, the communication module determines the communication capability and scope of application of the card reader, and its development is also accompanied by the progress of information technology, and continues to evolve in the direction of more efficient, more convenient and more intelligent.