CertiGuide to A+ (Core Hardware)  9  Chapter 0111:  Peripheral Devices       9  V  Keyboards

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Capacitive keyboards first arrived with the introduction of laptop computers. Because mechanically switch keyboards were too bulky and required too much power, a new technology had been developed for use in laptops.

Capacitive keyboards eliminate the expensive, power hungry key switch. Instead they use two sheets of semi conductive Mylar material. A thin layer of air separates the sheets of material. Each key in the keyboard has a small plunger on the bottom of the key. When a key is pressed the plunger pushes into the sheets of Mylar, forcing them into contact. When the sheets come into contact, the small voltages running through each sheet change. The keyboard controller can tell which key was pressed by the amount of change detected in the voltages.

These keyboards have the advantage of been inexpensive to manufacture and lower power consumption. However they are impossible to repair should they be damaged. Because of their low cost to manufacture, they can easily be replaced for less than $50.

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