A mobile phone jammer is an instrument that produces a signal that is within the same frequency range that cell phones use. The competing signals will result in blocking off the transmission of the cell phone because of the interference. Any person who attempts to use a cell phone that is within the effective radius of the mobile phone jammer will lose their signal but will not be able to know that a jammer is the reason for the signal interruption. The only thing the cell phone user will see is poor signal strength.

Cell phone ownership has become universal and its usage so prevalent that people now make phone calls wherever they are. This practice – which can be quite loud sometimes – can be so irritating that some people have taken to using phone jammers to temporary silence a room filled with cell phone users. These jammers are small enough to fit in a pocket or purse that no one will notice if someone’s using it. There are even some establishment owners like restaurants, bars, theaters, and cinemas who become tempted to use these jammers to give their establishments a little semblance of quiet.

Mobile phone jammers are actually illegal in many countries. Only law enforcement agencies, the military and other government agencies are mandated by law to use mobile phone jammers. But despite being deemed a criminal offense, some people still use mobile phone jammers because it is hard to know when someone is using it. There are models that are so small, it is the same size of a cell phone itself.