A signal jammer is a device that blocks wireless communication by creating a sort of signal traffic jam. It can be used to disrupt cell phones, GPS, Wi-Fi, or other radio signals. Signal jammers work by emitting radio waves that interfere with the frequency bands used by wireless devices. They create a signal traffic jam that blocks all communication within a certain range.

There are different types of signal jammers based on their target devices, appearance, and techniques. Some common target devices are mobile phones, GPS, Wi-Fi, Bluetooth, LoJack, 4G, XM. Some common appearance types are drag box, backpack, hand-held and suitcase. Some common techniques are noise jamming and repeater jamming.