How to determine the need to plug in a double USB plug?

When the mobile hard disk power supply is insufficient, need to plug in the dual USB port power supply.

Indication of insufficient power supply:

1, plug in the USB cable, please first look at the mobile hard drive on the body of the light? It should be a state of green light.

2, the lack of electricity will only be connected to the computer will appear and there is a clear display, in the transmission of data will never appear "low power" situation, please rest assured

3, when the mobile hard disk connected to the computer, not recognized by the computer, or recognized, but can not be considered as "removable disk" (shown as "! or?" Device), this means that the power supply is insufficient, please plug in a dual USB port.