Startechcom usb adaptor cables startechcom icusb2321fis this icusb2321fis 1 port ftdi usb to serial rs232 adaptor cable with optical isolation from startechcom converts an available usb 11 or 20 port into an rs232 db9 port that can be used to connect monitor and control your serial devicesthe usb to serial adaptor features integrated optical isolation circuits and surge protection to protect your critical sensitive control equipment against electrical damage making it a viable soluti