When the current reaches the buzzer, you hear a buzz. The length of the buzz depends upon the length of time that the switch is closed. When you operate the switch, you are in control. You can send any message you choose. This was how the first telegraph worked.
Long wires can cause too much resistance for current to get through.
In order for messages to be sent for long distances over wires, a form of relay had to be invented. Relays meant that the current could be received and increased enough to reach the next relay. So, the messages were passed along the wire from relay to relay until they reached their destination. If signals do not arrive, have students try shortening wires until they are successful. Have them think about why messages move better along short wires.