Touch-Sensitive+Screens

Different kinds of touchscreen work in different ways. Some can sense only one finger at a time and get extremely confused if you try to press in two places at once. Others can easily detect and distinguish more than one key press at once. Examples of touchscreens are: > This works by a flexible upper layer of conducting polyester plastic bonded to a rigid lower layer of conducting glass and separated by an insulating membrane. When you press on the screen, you force the polyester to touch the glass and complete a circuit, a chip inside the screen figures out the coordinates of the place you touched.
 * **Resistive touchscreen**:
 * **Capacitive Touchscreen**: These screens are made from multiple layers of glass. The inner layer conducts electricity and so does the outer layer, so effectively the screen behaves like two electrical conductors separated by a capacitor. When you bring your finger up to the screen, you alter the electrical field by a certain amount that varies according to where your hand is. Capacitive screens can be touched in more than one place at once, adding multitouch capabilities.
 * **Infrared Touchscreen**: An infrared touchscreen uses a grid pattern of LEDs and light-detector photocells arranged on opposite sides of the screen. The LEDs shine infrared light in front of the screen—a bit like an invisible spider's web. If you touch the screen at a certain point, you interrupt two or more beams. A microchip inside the screen can calculate where you touched by seeing which beams you interrupted. An example of a product this is used in is a Sony Ebook reader.
 * **Surface Acoustic Wave Touchscreen**: This touchscreen technology detects your fingers using sound instead of light. Ultrasonic sound waves are generated at the edges of the screen and reflected back and forth across its surface. When you touch the screen, you interrupt the sound beams and absorb some of their energy. The screen's microchip controller figures out from this where exactly you touched the screen.
 * **Near Field Imaging Touchscreen**: This works by when you move your finger up close, you change the electric field on the glass screen, which instantly registers your touch. This is much more robust than some of the other technologies, NFI screens are suitable for rough-and-tough environments (like military use). Unlike most of the other technologies, they can also detect touches from pens, styluses, or hands wearing gloves.
 * **Light Pen Touchscreen**: This was a very early style of touchscreen which work completely differently to modern day touchscreens. In the old style touchscreens the picture was drawn by an electron beam that scanned back and forth, just like in a cathode-ray tube television. The pen contained a photoelectric cell that detected the electron beam as it passed by, sending a signal to the computer down a cable. Since the computer knew exactly where the electron beam was at any moment, it could figure out where the pen was pointing.

Touch screen devices are now becoming very popular and there are hundreds of devices that can be bought that are touch sensitive. These devices are most commonly smart phones and tablets such as the Apple iPhone and iPad. These are typical examples of touch sensitive devices, but there are many other similar devices that are touch sensitive.
 * Advantages**
 * They don't have buttons which could possibly break
 * Usually have simple interfaces
 * As there are no buttons, the screens can be larger
 * Most touch screens are dirt and dust resistant
 * They are also easy to clean


 * Disadvantages**
 * The screen has to be big enough to be convenient
 * The larger screens can reduce battery life
 * In bright sunlight, the screens can be very hard to read
 * Usually more expensive than other devices



Touch Sensitive Devices are a type of Input Hardware. **Click here for other Input Devices**