Canon Speedlite 600EX II-RT Manual (en)

Turning on the Power
To save battery power, the power will turn off automatically after approx. 
90 sec. of idle use. To turn on the Speedlite again, press the camera’s 
shutter button halfway or press the test flash button (flash-ready lamp).
When set as the master unit for radio transmission wireless flash 
photogprahy (p.58) or set for linked shooting (p.86), the time until auto 
power off takes effect is approx. 5 min.
By setting the power switch to <a>, you can disable the flash’s 
button and dial operations. It is useful when you want to prevent the 
flash function settings from being accidentally changed after you set 
If you operate a button or dial, <k> is displayed on the LCD panel. 
While the lock is active, the functions displayed above function buttons 
1 to 4, such as <[>, <@>, are not displayed.
When a button or dial is operated, the LCD panel illuminates for approx. 
12 sec (p).
During normal flash photography, when set as the master unit in radio 
transmission/optical transmission wireless flash photography (p.58/90) 
or when used for the master camera unit in linked shooting (p.84), the 
LCD panel illuminates in green.
When it is set as a slave unit in radio transmission/optical transmission 
wireless flash photography or when used for a slave camera unit in 
linked shooting, the LCD panel illuminates in orange.
For the LCD panel Illumination when set as the master unit during radio 
transmission wireless shooting, see page 71.
Auto Power Off
Lock Function
LCD Panel Illumination