Cell Jammers are originally developed by law of enforcement and military to interrupt calls by criminals and terrorists. Before discussing about how Jammer works let's know little about mobile network and mobile phones. Mobile communicates to its network using base station or cell tower. As mobile moves from place to place the signals are handed from one tower to another. Mobile phones are full duplex device which use different frequencies for sending and receiving.
Cell JammerA Jammer Blocks or jams mobiles from receiving signals from base station. Jammers are of different sizes. Small hand held jammer blocks all bands within 9 meters range and larger jammer blocks mobile communication within 9kms/5miles. Small Jammer uses battery of mobile and large has to be charged. Jammer blocks not only calls but also internet, messaging and even emergency calls.
How Cell Jammer Works?Jammers can work by either disrupting phone to tower frequencies or tower to phone frequencies. Jammer generally blocks signals coming from base station or cell tower because towers are placed far away and signals coming from that tower will have less frequency. Jammer sends radio waves along with same frequency that mobile uses causing enough interference with the communication between cell phones and towers making mobile unusable. Simply to say "Jammers block signal frequency by transmitting relatively high power signals (noise) on the same frequency. Because of this high power, a cell phone can’t identify the signal from tower and it keeps searching for signals".
Used - at places of worship, library to maintain silence, in Parliament to avoid disturbances and to prevent leakage of information, in Army to block calls by criminals and terrorists and in schools and colleges to blocks calls of students.
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