Abstract: A bistable actuator comprising a magnetic member moveably mounted, in a housing of magnetic material, for movement between two positions. In each position such member is positively located adjacent a respective permanent magnet. Pole piece means is centrally located between the permanent magnets and extending from said housing to adjacent the moveably mounted member preferably extending to within a slot formed in the member. A separate coil is located within the housing between the pole piece means and each permanent magnet for energization to at least counteract the magnetic flux produced by the adjacent permanent magnet and allow movement of the member.

Abstract: The invention relates to methods and apparatus for removing dust from, or preventing dust from being attracted to, record discs. This is achieved by giving a negative charge to the dust particles in the atmosphere in which the record disc is located. Record discs are normally negatively-charged and, accordingly, negatively-charged dust particles are repelled by the record disc. The negative charge on the dust particles is produced by injecting negative ions into the atmosphere. Such negative ions may be produced by any suitable high-voltage generator with its positive pole earthed and its negative pole connected to one or more discharge electrodes. Preferably a brush is provided to disturb the dust in the grooves and a pad is provided to pick up the dust. Thus the record cleaner may consist of a pivotally-mounted arm carrying a brush and a pad, said arm being mounted on apparatus for producing negative air ions.