In order to facilitate remote data communication between computers, external devices or intelligent instruments equipped with different standard serial interfaces, standard serial interfaces must be converted to each other. The converter is compatible with RS-232 and RS-485 standards and can convert single-ended RS-232 signals into balanced differential RS-485 signals. It has a built-in fast transient voltage suppression protector. This protector is designed to protect RS-485 interface. By using today's advanced TVS (TRANSIENT VOLTAGE SUPPRESSOR), this series converter can extend the RS-485 communication distance to 1.2 kilometers, without the need for external power supply. It adopts a unique "RS-232 charge pump" driver and does not need to initialize the RS-232 serial port. Power supply is available, with zero-delay automatic transceiver conversion inside. The unique I/O circuit automatically controls the direction of data flow without any handshake signals (such as RTS, DTR, etc.), thus ensuring that the data flow in RS-232 mode can run in RS-485 mode without any modification, which makes the device suitable for existing operating software and interface hardware. The converter baud rate is 300 - 115,200 bps. It can be applied between host computers or between host computers and microcontrollers or peripheral devices, forming a point-to-point or point-to-multipoint remote multi-machine communication network to achieve multi-machine response communication. It is widely used in industrial automation control systems, all-in-one cards, access control systems, consumer systems, attendance systems, parking systems, self-service banking system, bus toll collection system, highway toll station system, etc.