With this sensor you can detect water leakage. So great to put down with your washing machine, for example. As soon as he detects water, an acoustic and visual alarm will sound. He can therefore work without a controller. A nice thought, because you do not always have your smartphone with you. You can of course also send a notification to your phone. Detecting the water can be done in 2 ways: by the golden dots on the bottom of the sensor and the other way to use the probe. With the probe you can extend the sensor. Handy if you have to go to a somewhat difficult to reach place. A bracket is supplied to hang the sensor on the wall, for example.