When a sensor is activated, it registers changes in your house. Many types of sensors can be used as an expansion for, among other things, alarm systems. At the moment of detection, the sensor sends a message to the main station. This station makes sure you'll be notified of what's happening in your home via the app on your tablet or smartphone. It's common to link sensors of the same brand. If you're combining sensors of different brands, it's important to pay attention to the type of protocol.