Sciencetech 550-200q is an external 0-200W adjustable constant current power supply for QTH lamps. Being a linear power supply as oppose to a switching power supply, it produces a highly stabilized 12-24VDC noise free output. Although this power supply can be used on lamps rated from 0-10A (with a maximum voltage of 30V), each lamp should be powered at its labeled wattage for optimum performance. The current control is done with a knob in the front of the power supply or by supplying a voltage between 0 and 1 Volt to the back connector making this unit computer controlled. The unit accepts both 110-120VAC and 220-240VAC inputs.