A ground penetrating radar includes a signal generator, a return signal processor, a gate and an antenna. With respect to the opposing magnetic member facing the toner supporting side magnetic member and a downstream magnetic member disposed more downstream than the opposing magnetic member in a rotational direction, a magnetic force generated in a vicinity of both longitudinally end portions thereof is greater than a magnetic force generated longitudinally inside thereof. By applying a sub-threshold stimulus to two neighboring electrodes where the sum of the stimuli is above the threshold of perception, a perception is created in neural tissue between the two electrodes. A carriage is movably attached to the base.