A machine having two machine parts, of which one is able to be rotated relative to the other, in which light signals are transferred from the one part to the other part. The light signals are transmitted radially to the axis of rotation of the rotatable machine part. In a first embodiment a plurality of light sources couple light into an optical waveguide ring which is coupled out over the entire outer circle of the optical waveguide ring so that it is guaranteed that light signals reach a receiver arranged radially outside in each case. In another embodiment light sources couple light into optical waveguide structures, with branches of the optical waveguides guaranteeing that on the outer circle of the one component the exit points for light are sufficiently dense that for any given angular position of the rotatable component at least one of two receivers receives a light signal.