Canon SPEEDLITE EL-1 Advanced User's Manual page 130

About the LCD Panel Illumination
During radio transmission wireless shooting, the light on the sender's display panel will
either be on or off according to the charge status of the sender and receiver (flash group).
The sender unit's LCD panel illumination is lit when the sender unit and receiver units are
not fully charged. When the sender unit and receiver units are fully charged, the LCD panel
illumination will turn off after approx. 12 sec.
When the charging of the sender unit and receiver unit starts as you take pictures, the
sender unit's LCD panel will be illuminated again.
Caution
If the sender unit or any of the receiver units (firing group) are not fully charged,
< > will be displayed on the sender unit's LCD panel. Check that
< > is not displayed on the LCD panel, and take a picture.
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