Remote data communication between different standard serial interface with computer, external device or intelligent instrument, conversion to standard serial interface. The converter is compatible with RS-232, RS-485 standard, can convert the RS-232 signal single end balanced differential RS-485 signal, the communication distance of RS-232 converter can be extended to 1.2 km, no external power supply adopts the unique "RS-232 charge pump" drive, don't need to initialize the RS-232 serial port can obtain the power supply, a zero delay automatic transmit receive switching, automatic control and data flow direction of I/O circuit is unique, without any handshake signals (such as RTS, DTR etc.), so as to ensure that the RS-232 prepared in half duplex mode programs running in RS-485 mode without changes, ensure appropriate existing software and hardware interface, converter transmission rate 300-115.2Kbps. can be used in between, the main control machine control and single chip computer or peripheral constitute a point-to-point, point to multipoint remote multi computer communication network, realize multi machine response communication. Widely used in industrial automation control system, smart card, access control system, parking lot system, self-service banking system, the bus fee system, the dining hall meal selling system, employee attendance management system, highway toll station system etc..