Chapter 22 – Input Devices

Publisher Summary This chapter focuses upon input devices that designate locations and movements in space, including touch screen devices, light pens, graphic tablets, mice, trackballs, and joysticks, and some more novel technologies. These devices are all reasonably well suited to pointing or selection among items on a display and the input of graphical information. They are not well suited to alphanumeric data entry. Human factors considerations affecting the design and selection of the different devices are considered first. Comparative human performance and preference data are then presented to aid in the selection of an appropriate device for an application. A touch-screen device produces an input signal in response to a touch or movement of the finger on the display. There are two fundamental principles of touch-screen operation; either an overlay is contacted or beams projected across the screen are interrupted. In the first category are conductive, capacitive, and cross-wire devices. The conductive touch screen has two conductive layers, each with an electrode grid in both the X and Y directions. When pressure is applied, the two surfaces touch and a circuit is completed.