What Material Blocks Cell Phone Signals

Cell phone jammer devices were originally developed for law enforcement and the military to disrupt the communications of criminals and terrorists. The bombs that detonated a commuter train in Spain in March 2004, as well as the explosions in Bali in October 2002 and Jakarta in August 2003, were all powered by mobile phones. It was widely reported that in December 2003, a What Material Blocks Cell Phone Signals thwarted an assassination attempt on Pakistani President Musharraf. When President Bush visited London in November 2004, it was reported that British police considered using the cell phone jammer to protect the President's motorcade through London.

In a hostage situation, the police can control when and where the kidnappers can make phone calls. Police can block phone calls during a drug hunt so suspects cannot communicate outside the area. What Material Blocks Cell Phone Signals Can be used in areas where radio transmission is hazardous (areas with potentially explosive atmospheres) such as chemical storage facilities or grain elevators. Antenna System & Supplies Inc.'s cell phone jammer has its own generator and can block cellular communications within a 5 mile (8 km) radius. Companies use jammers to thwart corporate espionage by blocking voice transmissions and photo transmissions from camera phones. On the more questionable end of the legality spectrum, hotel chains have been rumored to install cell phone jammers to discourage guests from using their phones and force them to use in-room phones at high rates.