Canon SPEEDLITE EL-1 Advanced User's Manual page 216

If the ambient temperature of the modeling lamp becomes too high, the lamp may dim or
turn off.
Display Level 1 Level 2
Icon
On Off On Off
Brightness When setting maximum brightness: dimmed Off
Battery temperature increase warning
The mark below appears when the temperature of the battery rises. Subsequently, the
display returns to the same state as the temperature increase warning ( ).
216