How to use "signal" in a sentence

At this signal, which he had pre-arranged with his friends, three men armed with metal poles rushed into the room

Marius, however, who had been going to fire the gun as a signal for the police to arrive, shook so much that he almost fell off the cupboard.

There's something about Needles, something about trouble on Route Sixty-Six, and he tries to listen, but the signal is weak.

any information call..." and then the signal fails, and there is only the sound of the old classic engine and the silence of the desert.

It neither rang nor returned a busy signal; the line hissed emptily

No busy signal

'New attempts have been made to signal, but without success,' was how the evening papers later described it

A dozen signal lights went on as soon as they began to move, warning the waiting guns around Esher

But no human being saw as much of them as I did and lived to tell the story, and I can say that I have seen four, five or six of them slowly performing the most difficult work without sound or any other signal