RS232/RS422/RS485 converter is popullarly used in RS485 or RS422 based system connecting with computer which need communication between system and the computer via serial port, the serial port adopt RS232 method while the RS422 or RS485 adopt RS422 or RS485 method, so they need a converter to convert the signal which can be transmitted. RS232/RS422/RS485 converter comes in many forms, mainly devided as port powered and external powered, plus extra circuit protection, it is a stable and reliable device in RS232 to RS422 or RS485 system