Sony DCR-TRV720 Operating Instructions Manual page 110

Using the printer – Introduction
Checking the power supply
Be sure to use a fully charged battery or the AC power adaptor.
Printing is not possible if the battery is low. However, recording may be possible
depending on how much the battery power remains. The remaining battery time
indicator does not indicate the possible printing time.
If you press PRINT while the battery is low, the warning indicator, E, will be
displayed on the LCD screen.
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