A dynamic bass equalization circuit has an amplitude dependent gain that is dependent upon the audio electrical signal amplitude and a dynamically adjusted frequency response that varies with the amplitude dependent gain. The apparatus comprises a clock reference from which a digital time constant is correlated to the nominal time constant of the network. The protective structure, when connected, extending from the housing beyond a battery connected to the battery charger. Reacting the carbon donors with the oxygen donors includes applying waste heat recovered from an external heat source to the reaction of carbon donors and oxygen donor. During production of the tank, the partition plate is temporarily fixed to the tank main body by riveting the two projections in a state in which the partition plate has been inserted through the cutout of the tank main body, and the partition plate is brazed to the tank main body in a state in which the plate has been temporarily fixed. The valve includes a control piston that is movable at least to actuate a connection between the coolant circuit and the pump circuit.