Signal jammers are devices designed to disrupt communication signals, such as those used in cell phones, Wi-Fi, and GPS. They work by emitting radio frequency signals that interfere with the normal operation of these devices, preventing them from sending or receiving information. These devices are often used in specific situations, such as in military operations or to enhance security in sensitive areas. However, the use of signal jammers is illegal in many countries, as they can interfere with emergency communications and public safety systems.