The Unit measure and control the current from tow separates USB I/O Ports. Each Port can be powered from an USB Input Port or from an external 5V Power Supply. The display shows the measured current and voltage from the USB Ports and the state of warning level. Also the display shows the actual power source. The information is also available at the connector for the FTDI – TTL – 232R -5V – Cable. With the keys you can setup a warning and error level for the current and a level for the low voltage state. In the states “PG = Power Good” and “CL = current Limit” the Unit hold the USB Output Port active. The states “SB = Stand By” and “OC = Over Current” switch the Output Port off. The actual state is also shown with three states LED on the bottom side.