Can You Send a Secret Code With 1 Letter?
An evil scientist has locked you in his lair and hands you a single button that will send the letter 'A' back to the secret agency you work for. He tells you the button will only work once, and once you press it, it will continue sending the letter 'A' until you press again to stop. The only thing you can tell is how many A's have been sent before you hit stop.
You tell him that if you send the agency a message saying "help me", they will storm the lair and rescue you, and you have planned for such a situation with the agency beforehand.
He walks out laughing, scoffing that such a feat is impossible. Is the evil scientist right? If not, how can you do it!