Davis Cook Memo – iPod Touch_ Phone Screen The thing that sets the by bestt571

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									                                                                                       Davis Cook

                               Memo – iPod Touch/ Phone Screen

        The thing that sets the iPod touch apart from other iPod models is its touch-screen
interface. When you touch the screen, the iPod's circuitry detects the presence of your finger. It
keeps track of how many fingers you have on the screen and where you move them. It also
gives the iPod touch the capability of running apps.

       The iPod touch does this using a layer of capacitive material under a protective covering.
The basic idea involves taking advantage of the electrical properties of the human body. When
you touch a capacitive surface, the amount of charge it holds changes. This is why devices like
the iPod touch require you to touch them with your bare skin -- insulating materials like gloves,
pens and styluses don't cause the same changes in the capacitive circuitry.




There are two possible methods the iPod touch can use to measure changes in electrical states:

      Self capacitance: Circuitry monitors changes in an array of electrodes.
      Mutual capacitance: A layer of driving lines carries current. A separate layer of sensing
       lines detects changes in the electrical charge when you place your finger on the screen.
Regardless of which method the screen uses, you change the electrical properties of the screen
every time you touch it. The iPod records this change as data, and it uses mathematical
algorithms to translate the data into an understanding of where your fingers are. In the next
section, we'll explore what the iPod touch does with this data and how to navigate through its
features.

								
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