A cell phone jammer is a device that blocks transmission or reception of signals, usually by creating some form of interference at the same frequency ranges that cell phones use. A signal jamming device works by broadcasting “noise” on a specific radio frequency (depending on the type of jammer). This prevents anyone within the perimeter of the jammer to use those frequencies.

A mobile phone jammer or blocker is a device which deliberately transmits signals on the same radio frequencies as mobile phones, disrupting the communication between the phone and the cell-phone base station, effectively disabling mobile phones within the range of the jammer, preventing them from receiving signals