Touch screens works by the person that is touching the screen and there are three ways that the devise can tell that the screen is being touched...........
- Surface acoustic wave
The resistive system includes a normal glass layer that is covered with another resistive metallic layer. They held apart by spacers, and a scratch-resistant layer is placed on top of the layers. Then an electrical current runs through the two layers while someone is using/touching the devise. When someone touches the screen, the two layers make contact in the exact spot where someone has touched the screen. Once the coordinates have been noticed, a special driver translates the touch into something that the operating system can understand, for example how the computer can detect the mouse's when someone click's or a drag's.
Remeber its not just ipods,phones and ipads that have touch screens
The Capacitive System
Surface Acoustic Wave System
On the monitor of a surface acoustic wave system, two messengers (one receiving and one sending) are placed along the x and y axes of the monitor's glass plate. They are also placed on the glass. There are reflectors that can send messages to the corners. The receiving transducer is able to tell if the wave has been disturbed by a touch.