When a compressor apparatus is operated at a maximum displacement for 60 minutes or longer, an ECU controls a pressure control valve to gradually change the refrigerant pressure in a swash plate chamber in a manner that gradually reduces the displacement of the compressor apparatus. The locking mechanism also including an aft latching device for locking the tow bar leg in a deployed configuration, and a fore latching device for locking the tow bar leg in a storage configuration. A pair of cooling tubes having a flat shape is disposed to sandwich the electric part so that both sides of the electric part are cooled by a pair of cooling tubes. A lid is hingedly attached to the rear wall. The engagement element engages at least one of the series of ridges in a first position, wherein the top jaw and bottom jaw pivot about a first axis that extends though a longitudinal axis of the pin, and wherein the engagement element is moveable along the first axis from the first position to a second position wherein the engagement element does not engage any of the series of ridges. The sensors may be removably coupled with at least one of the plurality of electrode modules and may sense ERPs from the test subject.