An assembly for stabilizing an individual while exercising in a seated position, such as, but not limited to, a wheelchair. The front-end signal processing circuit includes a feedback loop made up of a luminance detectingdigitizing section and a black level clamp section, and clamps a black level of an output signal of an image sensor to a prescribed set level. Each of the windings starts from a neutral wire and winds around a first tooth to form a first tooth winding portion and then winds around an opposed tooth to form a second tooth winding portion with the crossover wire extending as a power wire.