USB-COMi-SI: USB to single serial port converter with a DB9 (9-pin male) connector. (RS-422/RS-485) Comes with a USB cable. This model supplies Optical Isolation & Surge Protection. Each RS-422/485 port is individually optically isolated with 2000 volt DC optical isolation. The optical protects your PC or notebook from spikes and surges on the RS-422/485 network, by converting the electrical pulse into an optical signal and then changing it back into an electrical pulse. Your computer is well protected, since the surges and spikes cannot cross the optical link. Each RS-422/485 port is individually protected by surge protector to withstand electrostatic discharge and power surges up to 25KV ESD. Surge suppression on all signals prevent damages caused by lighning and high voltage.