Cannot use multiple USB devices

When using the front of the chassis USB interface, a USB interface to connect the printer all normal, but then insert a U disk, the LED flashing, can not detect the U disk.

Front of the USB interface only weak power supply performance, mainly user-friendly USB disk, in the insertion of other equipment, there will be insufficient power supply. You can attach printers and other devices to the interface behind the chassis, and do not use extension cords for extended periods of time. If the problem can not be resolved, the power supply should be detected, if the power supply is insufficient, you can consider replacing the power supply.