Touch screens emerged in the second half of the 1960’s

Dr. Samuel C. Hurst invented the touch screen in 1971.

First gained visibility in 1972; PLATO project

Multi-touch technology.

Top polyester layer coated with a transparent metallic conductive coating on the bottom

Adhesive spacer Glass layer coated with a transparent

metallic conductive coating on the top Adhesive layer on the backside of the

glass for mounting

Voltage is applied to each corner Electrodes are spread uniformly

across the field. Touch finger draws current from each

side proportionally Controller calculates position of the

finger from the current

Canova Dual Touch screen Laptop from V12 Design

New XM touch screen display featured in 2009 Hyundai Sonata

Iphone 3GSCharlie Card dispensers

Resistive Surface Acoustic wave Capacitive Iphone Surface Capacitance Iphone Projected Capacitance Infrared Strain gauge Optical imaging Dispersive signal technology Acoustic pulse recognition

Capacitive touch-screens use a layer of capacitive material to hold an electrical charge; touching the screen changes the amount of charge at a specific point of contact.

Its touch-sensitive screen includes a layer of capacitive material, just like many other touch-screens.

However, the Iphone's capacitors are arranged according to a coordinate system.

Its circuitry can sense changes at each point along the grid.

This allows the phone to determine the location and movement of simultaneous touches in multiple locations

The Iphone's screen detects touch through one of two methods: Mutual capacitance or self capacitance. In mutual capacitance, the capacitive circuitry requires two distinct layers of material.

One houses driving lines, which carry current, and the other houses sensing lines, which detect the current at nodes.

Self capacitance uses one layer of individual electrodes connected with capacitance-sensing circuitry.

The Iphone's processor and software are central to correctly interpreting input from the touch-screen. The capacitive material sends raw touch-location data to the Iphone's processor. The processor uses software located in the Iphone's memory to interpret the raw data as commands and gestures.

Silverman, Jacob.  "What is the Apple iPhone?."  10 January 2007.  HowStuffWorks.com. <http://electronics.howstuffworks.com/iphone-qotd.htm>  30 November 2009.

Wilson, Tracy V.  "How the iPhone Works."  20 June 2007.  HowStuffWorks.com. <http://electronics.howstuffworks.com/iphone.htm>  30 November 2009.