Primary controller decentralised/locally installed control equipment for a generation set to control the valves of the turbine, based on the speed of the generator (see primary control). The insensitivity of the primary controller is defined by the limit frequencies between which the controller does not respond. This concept applies to the complete primary controller-generator unit. A distinction is drawn between unintentional insensitivity, associated with structural inaccuracies in the unit, and a dead band set intentionally on the controller of a generator.