| 摘要 |
Power management is provided in a user operated data input device utilizing proximity sensing and switching between three or more power states. Capacitive proximity sensing may be carried out by detecting a relative change in the capacitance of a "scoop" capacitor formed by a conductor and a surrounding ground plane, wherein charge is transferred between the "scoop" capacitor and a relatively large "bucket" capacitor, a voltage of the bucket capacitor is applied to an input threshold switch, and a number of cycles of charge transfer required to reach the state transition is determined. Switching between the power states occurs based upon the presence or absence of input activity, and an operation instrumentality (e.g., a hand) in close proximity to or contact with the device. In an optical surface tracking cursor control device embodiment, switching to and from a BEACON state, which provides a reduced flash rate of a surface illuminating light source, is carried out based upon a detected presence or absence of a trackable surface.
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