The present invention provides for applying electric impulse trains to a patient. A ditherer generates a plurality of indicia, each of the plurality of indicia corresponding to an impulse train. The ditherer is further configured to vary the time period between generating the indicia corresponding to the plurality of impulse trains. There is also a plurality of outputs for each of the plurality of indicia. Each of the two impulse trains are substantially 180 degrees out of phase with one another.