Cell phone jammers are devices that can be about the size of a cell phone that create a dead zone for phone service. A small device that is the size of a cell phone can create a dead zone on average between 50 and 80 feet. These devices are only legal for U.S. goveremnt angencies to use in the U.S. I dont agree on normal people being able to use this device. It would only cause annoyence to many people. If you just wanted to block the signal of the annoying guy next to you in line or somthing it will but it could also block some one 50 feet away in there car tying to make an important phone call. They should only be used in emergemcy situations by police or other law enforcement officers. If kids get a hold of these things they would probly run around and try to see who they can annoy by blocking cell phone service. They invade other peoples prvicy. Who says its ok to block the annoying guy in line phone service, he could be having a very important conversaion with some one. These devices should not be legalzed in the U.S. unless there is a lot of restrictions made to control their use.