Canon SPEEDLITE EL-1 Advanced User's Manual page 38

About the Lock Function
By setting the power switch to <
operations. This is useful when you want to prevent the flash function settings from being
accidentally changed after you set them.
If you operate a button or dial, <
Note
You can directly fire a test flash and the modelling light even if the power switch is
in the <
illuminates.
>, you can disable the flash's button and dial
> is displayed on the LCD panel.
> position. Also, when a button or dial is operated, the LCD panel
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