Cell phones are everywhere these days. According to the Cellular Telecommunications and Internet Association, almost 195 million people in the United States had cell-phone service in October 2005. And cell phones are even more ubiquitous in Europe.

　　Unfortunately, restaurants, movie theaters, concerts, shopping malls and churches all suffer from the spread of cell phone jammer because not all cell-phone users know when to stop talking. Who hasn't seethed through one side of a conversation about an incredibly personal situation as the talker shares intimate details with his friend as well as everyone else in the area?

　　While most of us just grumble and move on, some people are actually going to extremes to retaliate. Cell phones are basically handheld two-way radios. And like any radio, the signal can be disrupted, or jammed.

　　Disrupting a cell phone is the same as jamming any other type of radio communication. A cell phone works by communicating with its service network through a cell tower or base station. Cell towers divide a city into small areas, or cells. As a cell-phone user drives down the street, the signal is handed from tower to tower.

　　A jamming device transmits on the same radio frequencies as the cell phone, disrupting the communication between the phone and the cell-phone base station in the tower.

　　It's a called a denial-of-service attack. The GPS jammers denies service of the radio spectrum to the cell-phone users within range of the jamming device.