Casio 3069 Manual page 101

• Illumination is disabled during time calibration signal reception, while
configuring sensor measurement mode settings, and during bearing sensor
calibration.
About the Auto Light Switch
Turning on the auto light switch causes illumination to turn on, whenever you
position your wrist as described below in any mode.
Note that this watch features a "Full Auto EL Light", so the auto light switch
operates only when available light is below a certain level. It does not
illuminate the display under bright light.
• The auto light switch is always disabled, regardless of its on/off setting,
when any one of the following conditions exists.
While an alarm is sounding
During sensor measurement
While a bearing sensor calibration operation is being performed in the
Digital Compass Mode
While a receive operation is in progress in the Receive Mode
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