Cell Phone

Cell phone jammers are devices that create a temporary "dead zone" to all cell phone traffic in their immediate proximity. Jammers are typically used by the police and military to control or disrupt communication during hostage situations and bomb threats. Traditionally, jammers were large antennas mounted on trailers that had to be pulled behind a truck. They now come in a variety of shapes and sizes including models that are about the size of a cell phone.
Now cellphone jammer is used in a variety of settings: schools, hospitals, prisons, restaurants, theaters, churches, etc.