It is used along with motorized single-phase or three-phase dimmerstat, which feeds either direct loads or the primary of a power transformer. The secondary of the transformer feeds any kind of useful load. The load voltage and current signals are fed back to the controller, and the controller settings regulate these quantities. Any physical parameters, like temperature or flow, which are linearly related to output voltage or current, also get indirectly controlled. This is a simple and economical, though somewhat crude method of control. Output regulation is 3%, and response time is in seconds.