| 摘要 |
The solar battery includes a plurality of cells having a same electromotive force with each other. The display device further includes a display means to display time, and a control means to control operation of the display means. The electromotive force of the solar battery is lower than a deterioration-start voltage of the rechargeable battery. The electromotive force of the cells is higher than a lower-limit driving voltage of the display device, in which a number of such cells equals a total number of cells include in the solar battery minus one. A driving voltage of the display means is lower than the aforementioned lower-limit driving voltage, and an operational voltage of the control means is lower than the aforementioned lower-limit driving voltage. |
