People or things that send signals.
Signalers are important because they help us understand things or make decisions.
Examples:
The lighthouse is one of the signalers for ships.
Animals can be signalers for natural disasters.
The alarm clock is a signaler that tells us when it's time to wake up.
The smoke from the fire is a signaler that something is wrong.
The bright colors of the flowers are signalers that they are good for the bees.
The traffic lights are signalers for the cars to stop and go.