using variable impedances in parallel with the load as final control devices

Full Title

Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems > Regulating voltage or current (G05F1/02 takes precedence) > wherein it is irrelevant whether the variable actually regulated is AC or DC > using variable impedances in parallel with the load as final control devices