| 摘要 |
A switchable magnetic device with first and second permanent magnets (10, 11 ), mounted within a housing such that the magnets (10, 11) are rotatable relati ve to each other, between a "fully off" position in which the north and south poles of the magnets are in substantial alignment with the south and north poles respectively of the second magnet, the device thus presenting a relatively weak external magnetic field, and a "fully on" position in which the north and south poles of the first magnet are positioned substantially i n alignment with the north and south poles respectively of the second magnet, the device presenting a relatively strong external magnetic field. Biasing means (30) are operatively associated with one or both of the magnets (10, 1 1) to bias the relative rotation of said magnets toward the fully on position, and wherein placing said device on or in close proximity to a ferromagnetic material causes magnets (10, 11) to rotate to a relative orientation such th at the device presents a relatively strong external magnetic field.
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