Why does Echo keep flashing the light on top all the time?

[Grannybuttons]

I tried using Echo as a clock radio last night, telling it to switch on the radio at 7am.
It did so, exactly as ordered. But all night it kept flashing the light on top, every so often waking me, & I could find nothing in Help that told me how to switch the blighter off!
Why does the light come on? Even when I was asleep.