Currently on the market popular UHF readers often provide a serial communication connection, and the serial port is the hardware and computer communication of the most important method.

Serial port is characterized by simple communication lines, as long as a pair of transmission lines can achieve two-way communication,serial communication distance can be from a few meters to a few kilometers; according to the direction of information transmission. Serial communication can be further divided into simplex, half duplex and full duplex three.

The initial serial port was used to connect computer peripherals, and was generally used to connect a mouse and an external Modem, as well as old cameras and writing boards. Due to the interconnection and data transmission between the two computers, a serial port can also be used.

At present, the connection between UHF RFID reader and computer is as follows: serial port RS232, RS485, Wiegand 26/34/42, RJ 45, WIFI, etc. Among them, RS-232, also known as standard serial port, is the most commonly used serial communication interface. It uses unbalanced transmission, the so-called single-ended communication. The maximum transmission distance is about 15 meters, and the maximum rate is 20kb/s. RS-232 is designed for point-to-point, and the driver load is 3 to 7kΩ. Therefore, RS-232 is used for local communication between devices, and most of the card reader device connections are also based on the 9-pin standard RS232 interface.