At the scheduled time, the light units will turn on and off gradually, simulating the different phases of the day (sunrise and sunset). With the intensity regulator, you can vary the intensity between 0% and 100% depending on the species of plants and fish you have. If more than one light unit is used, be sure to check that the current of the transformer corresponds to the current required for these light units. For example, for two 2.5A luminaires, a 5A (12V and 24V) transformer is required.