An a-Si film 12 is formed on the whole surface of a quartz substrate 11, and a protection film 13 is formed in a region to be used as a display unit on the a-Si film 12. The dischargeable storage device includes a deck having a pair of pivotable trap doors. The converter unit determines when to draw power from an external power and when to cease drawing power from the external power source by detecting a power enablement condition or a power disablement condition.