A dental device having at least one pneumatically operable handpiece, the
rotational speed of which can be influenced by a control element designed
as a foot-operated switch, and a further handpiece, which can be driven by
means of an electric drive, and the compressed air present at the
pneumatic handpiece influences the control of the electric drive. A
graduated filter is mounted on a pneumatically actuated hollow body and
the graduated filter has regions thereon which can be sensed by a light
barrier generating an electric signal in dependence on the properties of
the regions.