Disclosed is a method and apparatus for transmission of audio signals over a dedicated video transmission line in which the analog audio signal is inserted into and becomes a part of the video signal. The multiplication region, in operation, has a first ionization rate for electrons and a second, different, ionization rate for holes. The concentration of the gold and the platinum group metal is sufficient to enable oxidation of carbon monoxide and nitric oxide. Also disclosed is a complete toroidal vortex vacuum system employing a centrifugal dirt separator.