The standard RS-232 protocol has been widely used in most of industrial equipments for serial port communication. The USB interface also has been built in the personal computer or embedded system device. RS-232 and USB offer better transmission speed, wide range and networking capabilities. Hence, the AMC-2120, USB to 2-port RS-232 converter takes the important interface and popular to be deployed in the industrial communication network and higher reliable applications. It provides complete signal conversion between USB and RS-232 protocol.