It looks like you're using an Ad Blocker.
Please white-list or disable AboveTopSecret.com in your ad-blocking tool.
Some features of ATS will be disabled while you continue to use an ad-blocker.
Jammers block cell phone use by sending out radio waves along the same frequencies that cellular phones use. This causes enough interference with the communication of cell phones and the towers to render the phones unusable. On most retail phones, the network would simply appear out of range. Most cell phones use different bands to send and receive communications from towers. Thus jammers can work by either disrupting phone to tower frequencies or tower to phone frequencies. Smaller handheld models block all bands from 800MHz to 1900MHz within a 30 foot range. Small devices tend to use the former method, while larger more expensive models may interfere directly with the tower. The radius of cell phone jammers can range from a dozen feet for pocket models to kilometers for more dedicated units. The TRJ-89 jammer can block cellular communications for a 5-mile (8 km) radius. 
Older jammers sometimes were limited to working on phones using only analog or older digital mobile phone standards. Newer models such as the double and triple band jammers can block all widely used systems (AMPS, iDEN, GSM, et al) and are even very effective against newer phones which hop to different frequencies and systems when interfered with. As the dominant network technology and frequencies used for mobile phones vary worldwide, some work only in specific regions such as Europe or North America.
Originally posted by orangetom1999
Very intresting device. I understand how it would interfere with the duplexing signal ..either to or from the towers.
What I want to see is a device which will shut down a car with a loud stereo..either by shutting off the car or burning out the finals on a stereo system. I tire of being assaulted by loud stereos at stop points on the roads. It would be great to have silence or at least some relief from this assault by others.
Cell Jammers are big business in the private sector now.
Many many hotels use them to force patrons to use the hotel phones rather than making calls on there mobiles. It is illegal in the UK for hotels to use these but they do.