I phone features

Multi-Touch

With its large Multi-Touch display and innovative software, iPhone lets you control everything using only your fingers. How does it work? A panel underneath the display’s glass cover senses your touch using electrical fields. It then transmits that information to an LCD screen below it. The display also features an oil-resistant coating that keeps the iPhone screen clean.

Accelerometer

iPhone responds to motion using a built-in accelerometer. When you rotate iPhone from portrait to landscape, the accelerometer detects the movement and changes the display accordingly. The accelerometer also gives you amazing game control.

Sensors

When you lift iPhone to your ear, the proximity sensor immediately turns off the display to save power and prevent accidental dialing. The ambient light sensor in iPhone automatically brightens the display when you’re in sunlight or a bright room and dims it in darker places.

Location Services

GPS (Global Positioning System) technology uses information from earth-orbiting satellites to find locations. A-GPS (Assisted GPS) on iPhone 3GS goes a step further, finding the closest satellites to more quickly identify your position. If you’re not within a clear line of sight to a GPS satellite, iPhone finds you via Wi-Fi. If you’re not in range of a Wi-Fi hotspot, iPhone finds you using cellular towers. The size of a location circle tells you how accurately iPhone is able to calculate that location: The smaller the circle, the more accurate the location. iPhone also offers a built-in digital compass that automatically repositions maps to match the direction you’re facing.1

3G

3G technology gives iPhone fast access to the Internet and email over cellular networks around the world. With support for 7.2Mbps HSDPA, iPhone 3GS also makes it possible to do more in more places: Surf the web, download email, get directions, and watch video — even while you’re on a call. Since iPhone seamlessly switches between EDGE, faster 3G, and even faster Wi-Fi, you always get the fastest connection available. You can even share your Internet connection with your laptop via Internet tethering.2

source: http://www.apple.com/iphone/iphone-3gs/high-technology.html