Cell Jamming....

A Jamming device transmits on same radio frequencies as cell phone, disrupting communication between the phone and the cell phone base station in the tower.
Where Cell phone jammers are used?
Cell phone jamming devices are originally developed for law enforcement and military to interrupt communications by criminals and terrorists & during hostage situations and areas where radio transmissions are dangerous.
To get more information on Cell jamming watch IICM Forum-1.

By
J.L.Srinivas,
D.Sravan,
G.Karthik.