touchpad

hardware (Or "trackpad") A stationary pointing device used

mainly on laptop computers. Touchpads provide a small, flat

surface that you slide your finger over using the same

movements as you would a mouse. They were originally

developed to provide a more natural and intuitive connection

for the computer user than the mouse.

Touchpads use a principle called coupling capacitance, and

requires a conductive pointer such as a finger. They

contain a two-layer grid of electrodes which are connected

to an integrated circuit (IC) mounted under the pad. The

upper layer contains vertical electrode strips while the lower

layer is composed of horizontal electrode strips. Capacitance

from each of the horizontal electrodes to each of the vertical

electrodes is measured by the IC. A finger near the

intersection of two electrodes modifies the capacitance

between them, since a finger has very different dielectric

properties than air. The position of the finger is precisely

determined based on these changes at various locations.

According to one correspondent, you can use any part of your

body, which is not surprising, but not a McDonalds Chicken

McCrispy. You can use reheated Pizza Hut Christmas Pizza

though.

Synaptics .

(2000-11-01)