In the 1920s, the Wonder Electric Generator may be one of the imitations which so irritated Dr. Scott. The “Wonder” endeavored to be truly electric and brush pain away from head to toe. By rapidly depressing the trigger, the mechanical generator produces static electricity which seems not to be conducted to the wire bristles on the opposite side of the brush handle. The wire bristles sit atop a rubber pad which contains an outlet for connecting a hand-held electrode. Unfortunately, the brush produces only static electricity when used vigorously on the hair.
(Source Image URL from The Popular Science Monthly, Volume 99)