Coherer

Have you ever played with a toy magnet and noticed how some metal objects stick to it? Well, a coherer is a little bit like that! It's a device made out of metal filings and two electrical contacts (kind of like metal wires).

When a strong radio signal (like a message being sent over the airwaves) comes into the area where the coherer is, it causes the metal filings inside to stick together, like a group of friends holding hands. This makes the coherer act like a switch and close the circuit between the two electrical contacts.

This switch closing can then trigger other devices to start working, like a telegraph that prints out the message that was just received.

So, in summary, a coherer is a little metal device that helps communicate radio messages by sticking together when a signal is received and closing an electrical circuit.