an apparatus generates sine waves of electromotive force from a battery . the battery includes a given number of cells connected in series . a stator and commutator is formed by a multiple of segments . each of the segments is connected in sequence to a respective cell of the battery . the apparatus can be incorporated in a rotary switching device that further includes a rotor having at least one brush contacting the segments of the stator and commutator to carry a step waveform approximating a sine wave . the rotary switch can be included in various setups to provide a backup or alternate generator that provides alternating current .