A heat exchange system with a glycolwater loop to exchange heat with ambient air, and a second glycolwater loop that is in a heat exchange relationship to the ground and a system of refrigerant based ground source heat pump systems. The light emitting device includes a semiconductor layer, and a light extracting layer arranged on the semiconductor layer and made of a material having a refractive index equal to or higher than a reflective index of the semiconductor layer. The slope andor the height of edges of the envelope curve is continuously determined. The second switching output signal is delayed from the first switching output signal by a switching signal delay.