Patent ID: 7412770

Claim:
Device for adjusting the angle of a sighting unit to a target, in particular for a geodetic measuring instrument, comprising a sighting unit, which is rotatable about an axis, a reference base, at least one bearing for mounting the sighting unit to be rotatable relative to the reference base about an axis, a gear for adjusting an angle of rotation between the sighting unit and the reference base about the axis, and a clutch unit by which a torque flux about the axis can be at least one of limited or interrupted, the gear and the clutch unit being connected in series between the sighting unit and the reference base, and the torque flux around the axis between the sighting unit and the reference base occurring via the gear and the clutch unit, unless the torque flux is interrupted by the clutch unit, wherein the clutch unit has at least one electromagnet arranged around the axis for generating a magnetic field, and the torque flux around the axis can be at least one of limited interrupted by the action of the magnetic field.