Input or output with double tracks on 3.5 audio frequency for internet voice communication - LED indicator to check uplind/downpoet communication and OCP status easily - Each downstream port with OCD (over current detection) and OCP (over current protection) function - Self-powered mode mimicking, (driving + 5VDC total mini, 500mA from host PC) no external power source needed - USB1.1 and USB2.0 available -Working with windows 98/2000/XP/MAC OS 9.0 or Above