 Cell phone technology is progressing rapidly and changing the face of communications, so it's important to understand how a cell phone works. Cell phones are actually radios. They interface with the network in a full duplex system to transmit and receive radio signals. Full duplex means that there are separate channels sending and receiving information, so people can talk and listen to someone else simultaneously. This is in contrast to things like walkie-talkies that are half duplex where you can't hear the other person if you're talking. The network consists of low-powered radio antennas and transmitters arranged in cells. A cell is a certain geographic location that is served by a particular tower. If you are moving, your cell phone signal is transferred from cell to cell depending on your location in order to prevent you from losing the call. All of these cells are connected to a mobile switching center. Signals are passed from the phone through the antenna and sent through the switching center where they will either be passed to another cell or converted to a signal that can be sent along traditional telephone lines. The entire complicated process only takes a second to complete. Maintaining the system is very important to keeping the lines of communication open.