"e t=0 ms (and at a recurring rate thereafter) in order to realize the operation of channel 1 depicted, e.g., in the timing diagram of FIG. 3A. In a similar manner, the operation of channels 2, 3 and 4 shown in FIG. 3A may likewise be realized. [0112] As described, it is thus seen that any of the n electrodes may be assigned to up to k possible groups (where k is an integer corresponding to the num" . . . .