Importance

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Abstract

A trackball (10) is rotatably mounted on rollers (12, 14). The rollers are connected with rotational encoders (16, 18) for producing a series of pulses. Up/down counters (20, 22) convert the pulses into an indication of translation along two axes. Downward, non-rotational pressure on the trackball causes a transducer (B) to output an electrical signal which is recognizable as a selection signal. In some embodiments, the transducer is a strain gauge or other transducer (50) which provides an output whose magnitude varies with the amount of force. A comparitor (54) compares the output of the transducer with a selectable threshold to indicate whether a selection signal is to be issued. In other embodiments, the transducer has two states, e.g. a mechanical switch (70). The transducer changes states in response to the force on the trackball exceeding a preselected minimum.

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First Claim