7. The human interface device of claim 6 , wherein the foldable cover comprises a first electrode of the power source, and the first electrode is connected to a third electrode provided on the bottom surface of the human interface device when the foldable cover is mounted on the bottom surface of the human interface device.
8. The human interface device of claim 7 , wherein the bottom surface of the human interface device includes a groove where the foldable cover is coupled at a desired location.