danger signal

At the very moment of action, the man whom Rose had left at the floor-opening in the kitchen gave the danger-signal!

Is the use of a danger signal at a hazardous crossing, for the purpose of preventing disaster, pessimism?

By all poets and prophets the same danger signal shall be seen spreading before them both jogging along their old highways.

For long after his disappearance the mother otter anxiously studied the horizon for the tiniest danger-signal.

The hot blood of the Old South was pulsating in his veins and flaming darkly, like a danger signal, in his face.