| 摘要 |
<p>A projection display device has a power supply unit which supplies electric power from an external power supply, a charging circuit which charges a rechargeable battery with the power supply unit, an alarm part for outputting an alarm sound, and a switching circuit which supplies either the electric power from the power supply unit or an electric power from the rechargeable battery to the alarm part. When a voltage from the rechargeable battery becomes less than a threshold value, the electric power supply from the rechargeable battery to the alarm part is cut off, and power consumption of the rechargeable battery is suppressed.</p> |
