| Dr. Samuel C. Hurst invented touch screen monitors in | | | | measured by circuits and calculated by the computer |
| 1971 and since then they have become increasingly | | | | as to where the touch took place. The capacitive |
| popular, particularly in commercial computing such as | | | | system also allows a lot more light to be transmitted |
| ATMs and ticket machines and also in mobile phone | | | | from the monitor than the resistive system. |
| and PDA technologies. | | | | Capacitive touch screens are a lot more durable and |
| Touch screen monitors combine both an input and | | | | resistant to contaminant than the resistive system. |
| output device, minimising the need for separate | | | | They are a more popular for industrial and outdoor |
| peripherals like keyboard, mouse and monitor. Instead | | | | applications because of their durability and their |
| a user merely has to touch the monitor with either a | | | | imperviousness to moisture, dirt and grease. |
| finger or sometimes a stylus at manipulate the | | | | Surface acoustic wave technology uses ultrasonic |
| graphical user interface. | | | | waves that pass over the touch screen panel. When |
| Touch screen monitors use one of a number of | | | | the panel is touched, a portion of the wave is |
| technological systems to recognise a person's touch | | | | absorbed, like the current in a capacitive system and |
| the most common being resistive, capacitive, infrared | | | | this can be measured identifying the location of the |
| and acoustic wave. | | | | touch. |
| Resistive touch screens are the most versatile, they | | | | Surface wave panels can be easily damaged and |
| consist of a normal glass plate that is covered with | | | | contaminants on the surface will hinder its |
| both a conductive and a resistive metallic layers. The | | | | functionality but it offers higher clarity and optical |
| two layers are spaced apart and an electrical current | | | | accuracy than the other systems. |
| runs through them while the monitor is running. When | | | | Infrared touch screens employ two different |
| a user touches the screen, the layers make contact | | | | methods. One measures warmth of a person's touch |
| in that exact spot causing interference in the | | | | to the surface layer. This method requires warm |
| electrical field, the computer then calculates the | | | | hands and users cannot wear gloves or use a stylus. |
| coordinates. | | | | Another method is to use a light beam near the |
| The only downsides to this system are that the | | | | surface of the screen the infrared is used to |
| multiple layers restrict about a quarter of the light | | | | measure when that light beam is broken by touching |
| transmitted by the monitor and they can also be | | | | the monitor. IR touch screens are the most durable |
| easily scratched which reduces their efficiency. | | | | but can be slow to respond. |
| The capacitive system differs by having a layer that | | | | Other systems include strain gauge, where the |
| stores an electrical charge placed on the glass panel | | | | screen is spring mounted on the four corners and the |
| of the monitor. When someone touches the panel, | | | | movement is measured when the screen is touched. |
| some of the charge is transferred to the user, so | | | | This technology is heavily durable and resistant to |
| the overall charge on the layer decreases, this can be | | | | vandalism. |