The private signal was a challenge-and-reply code, changed every three months and known only to the King's ships in a particular area.

I think the first one is flying the private signal, but she's too far off to be sure.

"I assume the captain, because he had the copy of the private signals giving the challenge for the day."

But I am not happy about the private signal.

I shall be on deck directly: in the meantime make the private signal and our number.

"Hands about ship," said Jack, for the island's private signal was ten days out of date.

She patted my hand, then added a private signal I ignored, others being present.

In such a position, the correct answer to the private signal would be enough.

I must go below and look up the private signals.

Paul felt that he waited for some private signal from his sister.