The 203 is an industrial-grade, high-speed port powered, bi-directional 5000Vrms optically isolated RS232 3-wire isolator operates reliably up to 115.2K bps. The 203 is able to convert single-ended RS-232 signal to paired RS-485/422 signal and extend the communication distance to 1.2 km. No external power but adopts a particular RS-232 charge pump to drive the device, and gains electricity without initializing the RS-232 series interface. An internal zero delay auto transceiver and particular I/O circuit automatically control the data stream direction instead of a hand-shake signals (for example RTS, DTR etc).