The invention provides a hydrogen storage material consisting essentially of a hydride of lithium and magnesium, the material having the general formula: LixMgyHn wherein: x is in the range of from 0. The add-on slot may be a memory card slot. The integrator is applied regardless of the winner of the arbitration, and it is the only integrator used in the control method. The engine runs so quietly and burns so cleanly that in some applications it may not require a muffler andor a catalytic converter.