For communication between PC with different standard serial port and external equipment or intelligent instruments, where standard serial conversion is necessary. The GM-1004E-B converter is compatible with RS-232C, RS-485 standards. It converts RS-232 signals into balanced differential RS-485 signals. This converter is designed to protect an RS-485 port; as it adopts advanced TVS's (TRANSIENT VOLTAGE SUPPRESSOR). The transmission distance of RS-232 communication can be extended to 1.2km. It adopts unique “RS-232” charge boost technology to drive the system, and gains power without initializing the RS-232 serial port. This converter has built-in zero delay auto receiving, and transmitting conversion, offers unique I/O circuit with auto data flow direction without any handshake signal (RTU, DTR); this guarantees that there is no need to modify programming under RS-232, will run smoothly under current software and hardware. The transmission rate is 300-115.2kbps. It can be used between hosts, host and SCM, which building a point to point, point to multipoint long-distance communication networking. It is widely applied in industrial automation control systems, all-in-one cards, access control systems, parking systems, ATM systems, bus charging systems, canteen ticketing systems, attendance systems, and toll station systems, etc.