Signal Jammer THE 8 MOST ASKED QUESTIONS ABOUT SIGNAL JAMMERS: WHAT IS IT? What is a cell phone signal jammer? A mobile phone signal jammer ;is a device that blocks reception between cell towers and mobile phones. Developed for use by the military and law enforcement, these devices were originally created to combat threats like cell phone-triggered explosives and hostage situations. How do cell phone signal jammers work? Known as cell jammers, signal blockers, GPS jammers, or text stoppers, a cell phone signal jammer holds up the radio frequency in a given area, creating a sort of signal traffic jam that blocks all communication. Like a radio silence bubble, no calls or texts can be sent or received as long as the user is within range of the cell phone signal blocker. So, why are cell phone signal jammers used?