A LED display system includes a display controller including an output port having a first output terminal and a second output terminal; a plurality of LED sets; and a plurality of driving circuits, coupled in series and coupled between the display controller and the plurality of LED sets, respectively. The arithmetic average of shape coefficient SF-1 of the toner particles calculated by Equation 1 is from 125 to 170 and a ratio of that to an arithmetic average of the shape coefficient SF-2 of the toner particles calculated by Equation 2, SF-1SF-2, is from 1. A stationary plate and a movable plate resiliently contact, due to the action of a spring, over different contact areas as a movable shaft rotates. The tube may be flexed during the process, freeing solids trapped in the tube to flow through the center of the tube. The electrodes of the array are optimally located for discriminating EEG, FEMG and EM components from the recorded biopotential signals. The cleaning solution preferably includes hydrogen peroxide.