1. An electrical stimulator for biological tissus having output limits, comprising: storage means for storing a plurality of sets of stimulus parameters designed to specify an electrical stimulus signal comprising a plurality of pulses each having a pulse amplitude and a pulse duration; calculation means operatively coupled to said storage means for calculating the electrical charge which would be generated by each of said plurality of pulses contained in said electrical stimulus signal from said plurality of sets of stimulus parameters; limit means having a stored predetermined standard for the maximum electrical charge to be delivered by each of said plurality of pulses, said limit means being operatively coupled to said calculation means for comparing said calculated electrical charge of said electrical stimulus pulse with a predetemined standard and adjusting at least one of said plurality of sets of stimulus parameters so that said electrical charge of said electrical stimulus signal would not exceed said predetermined standard; generation means operatively coupled to said storage means, to said calculation means and to said limit means for taking at least one of said sets of stimulus parameteres as adjusted by said limit means and generating said electrical stimulus signal as designated by said and of said plurality of sets of stimulus parameters as adjusted.