riers. For these reasons, plus publicity about incomplete calls due to congestion on AT&T's network and lower prices for Android-based phones, the sales of phones running Google's Android operating system have surpassed iPhone sales. The advent of smartphones offers revenue opportunities from data applications as well as network challenges to carriers. Smartphone users now expect the same level of service for video and e-mail on mobile devices as they experience on desktop and laptop computers. They bring attention to the potential of mobile networks and to the need to upgrade them to keep up with the pace of data usage. Touch-screen Technology A Swedish company, Neonode Inc., introduced the first touch-screen mobile phone in March 2002. This innovative device had a 2-inch screen and used a different technol- ogy than that employed by Apple. Neonode's patented technology projects infrared beams in an invisible grid over the screen. Finger locations are detected as the beams are crossed. These screens respond to touch, finger motion, and stylus inputs. Neonode's phones were not widely adopted. In response, the company changed its business model from selling phones to licensing its screen technology to other com- panies. Neonode's technology can be used outdoors without glare. And it is for this reason that Sony selected it for its e-readers. It is also used in ATMs. For now, the technology is too costly for mobile phones, but Neonode is working on ways to lower its cost to make the technology viable for small, portable devices. Apple uses what is called capacitive technology for its touch screens. This tech- nology is used for BlackBerry devices, HTC Android phones, and Motorola Mobility's touch screens, as well. Capacitive touch screens use the inherent electrical properties of human fingers to determine where on the screen a user is touching. This is why nonelectric inputs such as a stylus or a hand in a glove cannot be used for input on these devices. A third touch-screen technology is called resistive. It cons