A tactile touch-sensitive device for use as an electronic input device for
navigating an electronic document on a display device is described. The
tactile aspect of the device provides a document location indicator, such
as a protrusion or a depression, which may be perceived through the sense
of touch. The device may incorporate additional features such as multiple
modes of navigation, namely isotonic and isometric scrolling. Various
sensors, such as force sensors and capacitive sensors, may provide the
user with coarse and fine scrolling capabilities through different types
of interactions with the scrollbar. The force sensors may allow the user
to alter the rate of scrolling by adjusting the magnitude of force
applied. Additionally, capacitive sensors may detect absolute positions
of a user's finger movement and navigate through a document pursuant to
those movements.