| In this chapter Touchscreen (or touch screen) monitors enable the user to transfer data into the computer by pressing onscreen icons. Touchscreen monitors are very popular in public-access and point-of-sale installations. Touchscreen monitors use CRT or LCD technology, which also incorporate one of the following surface treatments to make the monitor touch sensitive: -
Four-wire resistive technology ” Uses a glass panel coated with multiple layers that conduct and resist electricity. A flexible polyester cover sheet fits over the glass panel and is separated from the panel with insulating separator dots. The outer side of the cover has a durable coating; the inner side has a conductive coating. When the cover is pressed, an electrical signal is generated and is sent through the interface to the computer. The lowest -cost touchscreen technology, this type of screen is designed for public use. -
Five-wire resistive technology ” A more sensitive and more accurate version of four-wire resistive technology suitable for use by trained personnel (offices, point-of-sale, and so on). -
Surface wave ” Uses horizontal and vertical piezoelectric transducers to create ultrasonic waves. Touching the screen overlay disrupts the waves and the coordinates of the touch determine what signal is sent to the computer. Very durable surface able to compensate for surface damage and dirt. Suitable for self-service applications such as banking or information kiosks . -
Touch-on-tube ” Combines surface wave technology with direct touch contact to the CRT; no overlay is necessary. LCDs use an overlay with a simple air gap between the overlay and the panel surface. Suitable for self-service applications. -
Scanning infrared ” A light grid created by infrared (IR) signals is used to sense touches. Works with plasma as well as other types of displays. | | Touchscreens can also be retrofitted to existing CRT and LCD displays. However, this requires disassembly of the monitor, which voids the warranty and can be dangerous. See Chapter 13, "Safety and Recycling," for details about high-voltage hazards caused by the CRT's picture tube. | Touchscreens are available in freestanding versions similar to normal desktop CRT and LCD displays as well as in kiosk and built-in designs. |