There are two modes of operation that are selected by a switch on the front of the Lunar Cycle Simulator-Dim and Lunar. When the switch is in the dim position, the MoonCast LED lights can be manually dimmed between 0 and 100% by turning the control knob. When the switch is in the Lunar position, the intensity of the MoonCast LED lights varies each time the unit is powered up (timer required) over a 29 day "Lunar Month" resulting in a 29 step sinusoidal curve between 1% and 100%. Supplied with a 60 cm in-line lead.