Anyone who has flown for a long time knows the situation: one pilot flies, one pilot sleeps. And sometimes the pilot who is flying becomes a pilot who is sleeping, and that is a critical situation. Train drivers have a dead man's button that automatically brings the train to a halt if the button is not pressed. Why don't balloon pilots on night flights or long flights have a don't sleep button that wakes them up with a noise signal when they fall asleep?

Now you could simply use a short-time alarm clock. But then the pilot who is supposed to be asleep would always be woken up if the pilot who is flying fails to reset the short-time alarm before it rings.

It would therefore be better if the Don't sleep button were to be reminded to reset it with a light signal before the loud alarm signal.

The video illustrates how it works:

The video at Youtube