Casio DW-5600E Alarm Timer Chrono, Sep. 2007

The star-like Backlight icon (above the 20 seconds)
is not an Auto Light indicator. Even it is used as such on some other Casio models. Yet other Casio models use A.EL or a combination of AUTO and the star-like icon. The Backlight function of the Caliber 1545 illuminates the display when an alarm sounds or when the countdown timer reaches zero. It also flashes when the hourly time signal sounds. Of course, the hourly signal has to be turned on. This is the case in this picture, note the bell icon next to "SU".