US Patent 6944503 Method and apparatus for electrical stimulation

Pulsed electrical stimulation is applied to selected tissues via electrodes positioned on and/or in the body. Each electrode is connected to an output (108) of the apparatus. Each output (108) is connected between a high side switch (110) and a low side switch (112) of a switching array. Each stimulation pulse is subdivided into a number of time periods. By operation of the switches (110, 112) each electrode can be selected to operate as an anode or a cathode or neither during any given time period. The spatial and/or time summation of the anode-cathode currents is controlled to selectively to stimulate selected regions and/or types of tissues, typically nerve tissues.