Sony XAV-C1 User Manual page 68

Scroll: You can scroll by moving the pointing device while holding
down the center button, without using the scroll bar.
Zoom: To drag the zoomed picture, move the pointing device while
holding down the center button. To change the zoom percentage,
click while holding down the center button. To change the zoom size,
right-click while holding down the center button.
Not used: Check when neither of the functions is used.
When you set the pointing device sensitivity to high, the pointer may move across the
screen on its own. This is called a "drift" and is not a malfunction. The pointer stabilizes if
you do not touch the pointing device for a few seconds.
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