Thyristor Panels for the Air Handling Unit heaters deliver smooth, proportional control of the temperature. For larger heater capacities, the most effective solution is a hybrid approach—combining step control stages with thyristor modulation. Step stages (contactors) handle coarse load levels, and the Thyristor fine-tune the output within each step. Will normally include auxiliary control circuits, in addition to filter fans for cooling (one with thermostat and a space heater controlled by humidistat), and motion operated panel light.