Abstract: Apparatus (20) comprising magnetic means in the form of a magnet (22) which is spaced in use from the surface of an object such as a roof R of an emergency Vehicle for example a police car or the like by resilient spacer means in the form of an “O” ring sealing member (24). The magnet (22) is connected to an article such as a light or siren (28) used by emergency services such that the light or siren (28) can be mounted on a vehicle V as required.

Abstract: There is disclosed a grinding machine in which a component of circular cross-section is capable of being ground, the component being supported at points on its periphery during grinding, said machine including (i) an analysing means whereby periodic irregularities in the periphery of the component as it is being ground may be detected and analyzed to determine the periodic adjustment in the position of the component necessary to eliminate, during grinding, the detected periodic irregularities, said analyzing means including means for producing a signal indicative of the adjustment necessary and (ii) means for periodically adjusting the position of the component in response to the signals from the analyzing means thereby to cause said periodic irregularities to be eliminated.